I have an Azure AD in which I have some users that are sourced from a another Azure AD. I have no problem authenticating these users from my MVC web application using OpenID Connect Owin middleware, but when trying to get user profile by querying https://graph.microsoft.com/v1.0/me in the Microsoft Graph API, I get a NotFound result. The user name (email) in the error message is with an underscore instead of an @ sign.
Getting user profiles for users within the original AD works just fine.
Any ideas? Is this a known issue and is there a way to get around it?