Login Broken After Migration

Howdy all,
Our app has been broken for over 6 weeks, ever since the move to the new backend architecture. We have certain users (but not all users) who when they login receive an invalid email or password message, despite using the correct credentials. This happens both with SSO and with local Knack login (when using the same email address). Knack is no longer responding to the help ticket about this or our other issues post-migration (and there are many). So, I’m turning to the community.

Has anyone else experienced this kind of issue? If so, have you come up with a resolution?

Sorry to hear that support are not responding to you. I’m aware that they are very stretched. I’ve also been experiencing extended response times.
All my client apps have been migrated (circa 30+) and I’ve not heard of this particular issue.