I see ...-cai.icp0.io": Failed to fetch which likely means that the icp0.io is blocked for some users resulting in II being unable to fetch a needed file to proof the derivation origin.
A while back the domain was inadvertently listed as spam domain: [Resolved] Icp0.io listed in Spamhaus DBL
This has since been resolved, but it’s likely that their internet provider has not updated its spam list yet to remove the domain again or has its own strict spam list.
I would recommend these users to try a different DNS than their internet provider and see if that resolves the issue, here are some options: