Since last week around February 24 we have been unable to login using our B2C tenant (Europe). Until a few days ago it was working sometimes, but since yesterday we had no success at all.
We mostly receive "Sorry, but we're having trouble signing you in" with "An exception has occurred". Application Insights only show Activity Type="Issue an id_token to the application" and Status Reason="There is a problem with the service.".
If we actually do succeed logging in and redirecting to our app, the 3 returned cookies x-ms-cpim-* contains mostly no value AND always an expiration date exactly 10 years ago.
We tried multiple user accounts/client PCs/browsers, increasing token/cookie lifetimes and reverting to last known working custom policy XMLs and app code.
Update:
We have another B2C tenant that is working too and it seems to return 10 year old cookies as well, so probably not the issue.
But when our faulty B2C tenant sometimes successfully signs in, apparently our app is unable to use whatever is returned from B2C. Identity Server 4 GetAuthorizationContextAsync() returns null