# Help: ICP Gateway returns Error 400 Unknown Domain **URL:** \ **Category:** Developers\ **Created:** [September 7, 2025, 1:57pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948 "2025-09-07T13:57:33Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![ICExplorer\_io](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/icexplorer_io/32/21916_2.png) [@ICExplorer\_io](https://forum.dfinity.org/u/ICExplorer_io)\ **Post date:** [September 7, 2025, 1:57pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/1 "2025-09-07T13:57:33Z")
Since yesterday, we found that our website deployed on ICP has stopped working, and the page shows: Error 404 Unknown DomainThe requested domain is not served by this HTTP gateway. Please check that the address is correct. ![telegram-cloud-photo-size-5-6192882313419933480-y](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/d/b/db6356b9196e0f7836b5c0486aaa2739e9a3980b.jpeg) Following the documentation [https://internetcomputer.org/docs/building-apps/frontends/custom-domains/using-custom-domains#step-1-configure-the-dns-record-of-your-domain-which-is-denoted-with-custom\_domain](https://internetcomputer.org/docs/building-apps/frontends/custom-domains/using-custom-domains#step-1-configure-the-dns-record-of-your-domain-which-is-denoted-with-custom_domain) we reconfigured the DNS records and verified the DNS resolution: ```auto ➜ ~ dig CNAME _acme-challenge.www.icexplorer.io +short ``` ```auto _acme-challenge.www.icexplorer.io.icp2.io. ``` ```auto ➜ ~ dig TXT _canister-id.www.icexplorer.io +short ``` ```auto "sitc5-eiaaa-aaaal-qjnna-cai" ``` ```auto ➜ ~ ``` After that, we submitted the registration. While waiting, we checked the registration status, and it showed `PendingAcmeApproval`. Sometimes, it also showed `PendingChallengeResponse` and Failed. ```auto ➜ ~ curl -sL -X GET https://icp0.io/registrations/9367c ************ ``` ````auto {"name":"www.icexplorer.io","canister":"sitc5-eiaaa-aaaal-qjnna-cai","state":{"Failed":"order is unable to reach 'Ready' status"}}%``` ```` What could be the cause of this issue, and how can we fix it? ---
**Author:** ![bitel911](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/bitel911/32/29385_2.png) [@bitel911](https://forum.dfinity.org/u/bitel911)\ **Post date:** [September 7, 2025, 6:55pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/2 "2025-09-07T18:55:22Z")
> [@ICExplorer\_io](#): > > `www.icexplorer.io"` ![Scherm­afbeelding 2025-09-07 om 20.52.07](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/1/c/1cac4fffedcfb19af6ba1641a487251ae3433249.png) ![Scherm­afbeelding 2025-09-07 om 20.52.27](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/9/8/98166f94cc08ff636bd4220250d23039d807c99c.png) Seems to be the same issue with SSL like that one with the id.ai here [Internet Identity id.ai outage / SSL certificate - #6 by lmuntaner](https://forum.dfinity.org/t/internet-identity-id-ai-outage-ssl-certificate/53995/6) @lmuntaner Do you have any idea if it is the same ? ---
**Author:** ![tomkoom](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/tomkoom/32/15996_2.png) [@tomkoom](https://forum.dfinity.org/u/tomkoom)\ **Post date:** [September 8, 2025, 3:35am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/3 "2025-09-08T03:35:39Z")
Have the same issue for the [cyql.io](http://cyql.io). It was working fine just recently with the set-up from: [https://internetcomputer.org/docs/building-apps/frontends/custom-domains/using-custom-domains](https://internetcomputer.org/docs/building-apps/frontends/custom-domains/using-custom-domains). Now the domain shows “Your connection is not private”. After attempting to re-register the domain, I get: ```auto {"name":"cyql.io","canister":"n7ib3-4qaaa-aaaai-qagnq-cai","state":{"Failed":"order is unable to reach 'Ready' status"}} ``` ---
**Author:** ![tomkoom](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/tomkoom/32/15996_2.png) [@tomkoom](https://forum.dfinity.org/u/tomkoom)\ **Post date:** [September 9, 2025, 1:25am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/4 "2025-09-09T01:25:41Z")
Would love for some fresh eyes from the community & devs on this issue. ---
**Author:** ![MathewTas-007](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/mathewtas-007/32/29612_2.png) [@MathewTas-007](https://forum.dfinity.org/u/MathewTas-007)\ **Post date:** [September 9, 2025, 3:28am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/5 "2025-09-09T03:28:25Z")
Interesting to see this come up — I’ve been experimenting with deploying through ICP Ninja recently, and I’m also hitting a dead end, but in my case, it’s a simple 404 Page Not Found right after deployment. Could the gateway/domain configuration changes you’re mentioning also affect Ninja-hosted deployments, or is this more specific to custom DNS setups? 🤔 Just trying to figure out if the two issues could be related before I start digging deeper. ---
**Author:** ![tomkoom](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/tomkoom/32/15996_2.png) [@tomkoom](https://forum.dfinity.org/u/tomkoom)\ **Post date:** [September 9, 2025, 5:06am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/6 "2025-09-09T05:06:11Z")
I think the issue might be not in the DNS setup, as it was working fine before with the same setup. Can’t say about ICP Ninja, I wonder as well. ---
**Author:** ![MathewTas-007](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/mathewtas-007/32/29612_2.png) [@MathewTas-007](https://forum.dfinity.org/u/MathewTas-007)\ **Post date:** [September 9, 2025, 5:15am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/7 "2025-09-09T05:15:25Z")
Yeah, I was just testing deployments on ICP Ninja and got a 404 too . Wondering if it’s something on their end or just me. ---
**Author:** ![nikolay.komarevskiy](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/nikolay.komarevskiy/32/18487_2.png) [@nikolay.komarevskiy](https://forum.dfinity.org/u/nikolay.komarevskiy)\ **Post date:** [September 9, 2025, 12:16pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/8 "2025-09-09T12:16:55Z")
Hi @ICExplorer_io and @tomkoom The issues you encountered are entirely caused by the custom domains service and we are sorry for that. A certificate issuance task got stuck for several days and finally failed to complete. We have reached out in a DM to fix the issue. We are aware of these issues and are looking into it. At the same time, we are also working on a new, more robust version of the custom domains service, which is approaching production release soon. We are very sorry for these troubles happening meanwhile. ---
**Author:** ![bitel911](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/bitel911/32/29385_2.png) [@bitel911](https://forum.dfinity.org/u/bitel911)\ **Post date:** [September 9, 2025, 7:22pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/9 "2025-09-09T19:22:16Z")
![Scherm­afbeelding 2025-09-09 om 21.19.06](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/5/2/5230b41953ed1d6b1b4c8aa51c4a53fc129c38ac.jpeg) Hey @ICExplorer_io you had posted the backup link with canister url But the data is fetched from [api.icexplorer.io](http://api.icexplorer.io) whcih is not operational, any timeline on when you be able to server this? I am building some things with caffeine and was using ICE for the data in all my apps, any other alternativves in the mean time? > ---
**Author:** ![WebTreeSoftwareSolut](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/webtreesoftwaresolut/32/40772_2.png) [@WebTreeSoftwareSolut](https://forum.dfinity.org/u/WebTreeSoftwareSolut)\ **Post date:** [September 9, 2025, 7:41pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/10 "2025-09-09T19:41:19Z")
Hey @bitel911 their own site (from the canister link) is also failing to fetch the api data. Im sure theyre working on it! ---
**Author:** ![bitel911](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/bitel911/32/29385_2.png) [@bitel911](https://forum.dfinity.org/u/bitel911)\ **Post date:** [September 9, 2025, 8:41pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/11 "2025-09-09T20:41:38Z")
I know since i Comment on it 2 days ago but they tweeted out a link that was a backup and this also did not work, there was not any other information i could find at leats, that is why I shared it Yes hope it gets resolved so we can all enjoy their service again, IC explorer my favorite site for data ---
**Author:** ![ICExplorer\_io](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/icexplorer_io/32/21916_2.png) [@ICExplorer\_io](https://forum.dfinity.org/u/ICExplorer_io)\ **Post date:** [September 10, 2025, 2:49am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/13 "2025-09-10T02:49:31Z")
The domain’s back up now, thanks for all your hard work. ---
**Author:** ![tomkoom](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/tomkoom/32/15996_2.png) [@tomkoom](https://forum.dfinity.org/u/tomkoom)\ **Post date:** [September 10, 2025, 3:29am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/14 "2025-09-10T03:29:56Z")
[cyql.io](http://cyql.io) is still in `PendingAcmeApproval` state, after it switches to: `{"name":"cyql.io","canister":"n7ib3-4qaaa-aaaai-qagnq-cai","state":{"Failed":"order is unable to reach 'Ready' status"}}`, and restarts @nikolay.komarevskiy ![Screenshot 2025-09-10 at 10.22.30](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/0/0/004e26cbefdf30efa860f06099b9f6c97b99ec92.png) ![Screenshot 2025-09-10 at 10.23.35](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/d/8/d856b1d59fab84582788f37e48b1be9a32ee4bda.png) ![Screenshot 2025-09-10 at 10.23.42](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/3/6/36423eb32374eb4145304467ffd801646c2d5e0b.png) ![Screenshot 2025-09-10 at 10.23.59](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/9/c/9c6d5aa18dd8f735468cdc9269aac5fc4229d491.png) ![Screenshot 2025-09-10 at 10.24.07](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/6/9/69c050a451a1e5fac5db90184f9d5554d58a85d0.png) ![Screenshot 2025-09-10 at 10.26.17](https://us1.discourse-cdn.com/flex023/uploads/dfn/original/3X/2/0/20edd7edcfb19a474e9b52b7831c5c796f33d7de.png) ---
**Author:** ![brian](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/brian/32/21375_2.png) [@brian](https://forum.dfinity.org/u/brian)\ **Post date:** [September 30, 2025, 2:13am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/15 "2025-09-30T02:13:36Z")
hi we are also experiencing the same issue. Is there a place for us to find the custom domains service statuspage or similar? much appreciated and thank you for your help 🙏 ---
**Author:** ![rbirkner](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbirkner](https://forum.dfinity.org/u/rbirkner)\ **Post date:** [September 30, 2025, 7:27am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/16 "2025-09-30T07:27:41Z")
Hey @brian, can you please let us know what your domain name is. Then, we can look into it. ---
**Author:** ![brian](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/brian/32/21375_2.png) [@brian](https://forum.dfinity.org/u/brian)\ **Post date:** [September 30, 2025, 7:42am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/17 "2025-09-30T07:42:52Z")
thank you @rbirkner your help is very much appreciated, the domain is: [https://posted.app](https://posted.app) (it was functioning alright until quite recently which resulted in me needing to retry the whole custom domain process once more). For reference our icp subdomain pointing to the same canister (and configured with the same .well-known) continues to work just fine `https://icp.posted.app` Any insights/help is greatly appreciated! the current pending registration id is: [https://icp0.io/registrations/4e0f93062647094213e2eae6248d3755405ac3dda1ecccdad5604bf65f45c28e](https://icp0.io/registrations/4e0f93062647094213e2eae6248d3755405ac3dda1ecccdad5604bf65f45c28e) ---
**Author:** ![brian](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/brian/32/21375_2.png) [@brian](https://forum.dfinity.org/u/brian)\ **Post date:** [October 4, 2025, 9:51pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/18 "2025-10-04T21:51:59Z")
Just an update, after a couple more days (when the prior pending registration expired), I retried once more just now with the exact same steps and now it works. It does seem that there were indeed some intermittent issues with the registration that seem to have been resolved now. Not sure if there is a way to nail down what the root cause was but for anyone else in the future that comes across the issue, you may need to retry after a few more days for it to resolve. Cheers 👍 ---
**Author:** ![taimoor\_dev](https://sea1.discourse-cdn.com/flex023/user_avatar/forum.dfinity.org/taimoor_dev/32/30432_2.png) [@taimoor\_dev](https://forum.dfinity.org/u/taimoor_dev)\ **Post date:** [October 5, 2025, 9:18am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/19 "2025-10-05T09:18:08Z")
Had a similar issue recently — the registration was stuck in `PendingAcmeApproval` for days. What worked for me was simply waiting until the previous pending order expired, then retrying the setup. It went through successfully the second time. Seems like occasional hiccups happen with the custom domain service, so a short wait + retry can solve it. ---
**Author:** ![rbirkner](https://avatars.discourse-cdn.com/v4/letter/r/838e76/32.png) [@rbirkner](https://forum.dfinity.org/u/rbirkner)\ **Post date:** [October 5, 2025, 3:03pm UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/20 "2025-10-05T15:03:47Z")
I have posted some more insights/details in this thread. Have a look at these replies in particular: > [@Custom Domain Re-registration?](https://forum.dfinity.org/t/custom-domain-re-registration/58467/3): > > Hey @WebTreeSoftwareSolut and @Cris.MntYetti, we do experience some flakiness (especially with apex domains). Often the cause is that the domain is registered with Cloudflare and there is some misconfiguration. When you use Cloudflare, you need to make sure that you have disable edge certificates as it can interfere with the custom domains service. You can disable it the following way: Go to your domain in the cloudflare panel, then go to “SSL/TLS” → “Edge Certificates”, scroll all the way dow… > [@Custom Domain Re-registration?](https://forum.dfinity.org/t/custom-domain-re-registration/58467/6): > > The issue with these Edge Certificates by Cloudflare is that if enabled, Cloudflare also obtains certificates for the domain. To do so, Cloudflare also uses the ACME DNS-01 challenge just as our custom domains service does. We have observed now multiple times that sometimes Cloudflare fails to clean up the TXT records it sets and these then interfere with our custom domains service as Let’s Encrypt does not follow the redirect (CNAME to \_acme-challenge.your-domain.com.icp2.io) but just checks th… ---
**Author:** ![Nimakra](https://avatars.discourse-cdn.com/v4/letter/n/aeb1de/32.png) [@Nimakra](https://forum.dfinity.org/u/Nimakra)\ **Post date:** [October 7, 2025, 5:04am UTC](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948/21 "2025-10-07T05:04:48Z")
I tried reregistration. It’s stuck in `PendingAcmeApproval` as well. I’m using Cloudfare. I disabled Universal SSL, as recommended (though it had been working all along with that option enabled). `https://oraculumhub.com` `2kz4x-mqaaa-aaaan-qm3hq-cai` Infact, when I run `curl -sL -X GET \https://icp0.io/registrations/...` it alternates between `PendingAcmeApproval` and` "Failed":"order is unable to reach 'Ready' status"` [Next page](https://forum.dfinity.org/t/help-icp-gateway-returns-error-400-unknown-domain/56948.md?page=2)