Which browser are you using? Do you get the same exception if you try logging in from a private window?
I did not alter the default user attribute mapping for an OIDC IdP, which is a direct mapping to ‘sub’ for ID and username and no mapping configured for the other attributes.
Here are the steps I took to setup AAD as an OP for Ignition:
How to set up Azure Active Directory as an OpenID Connect Provider for Ignition.pdf (2.7 MB)