We just upgraded from 7.9.5 to 8.9 and all users get the following error. I just checked groups and users and all of them are still available and permissions are correct. I tried to add openid connect and gitlab connect but still getting the same error. New users trying to login are not shown in the users section. Any ideas?
Additional SAML checks (8.4)
SAML authentication adds additional checks for validating SAML responses from the identity provider. This could reveal a non-standard configuration that needs to be updated. Information will appear in the logs upon a failed login attempt in the event that the configuration needs to be tweaked.
I would advice you to check the server side logs (particularly web.log and access.log) for any error message and share it here.