How do I fix a missing directory error in Azure AD?
This error is usually caused when an Azure subscription is moved to a new Azure AD directory and the old Azure AD directory that's associated with Azure AD DS is deleted. This error is unrecoverable. To resolve the alert, delete your existing managed domain and recreate it in your new directory.
How do I resolve aadsts50020?
Solution: Sign out, then sign in again from a different browser or a private browser session. Instruct the user to open a new in-private browser session or have the user try to access from a different browser. In this case, users must sign out from their active session, and then try to sign in again.