A root-cause analysis for this issue has been performed and is now available at: https://cdn.auth0.com/blog/2024_11_26_Failing_Logins_for_Requires_Username_DB_Connection_Settings_Update.pdf
Our team has found the root cause: login field is type 'email' now. If our customers experience failing logins as a result - it was possible to login without '@' before - they can enable 'Requires Username' in the connection settings to properly configure the feature and fix the issue.
We are currently investigating an incident that impacted our services. Our team is actively working to understand the root cause and mitigate the issue. We will provide updates as we gather more information.