I identified the source of the problem as my oversight in overlooking the boundary security upgrade documentation. Following the recommendation, we made changes to the main base-domain in the request URL, but unintentionally left the canister id in the subdomain, which caused the request to be redirected incorrectly.
The original problematic URL was: https://<canister_id>.ic0.app/api/v2/canister//query
However, we successfully resolved the issue by using the correct URL:
https://ic0.app/api/v2/canister//query
Thank you for your valuable support!