AADSTS50020 - User account xxx from Identity provider does not exitst in tenant

Hello Community,

I´ve a very strange issue three users from my Azure AD Tennant.

Every user is synchronized from local active directory and have a valid license (E3 or E5 assigned)

Now to my problem:

Since a week or two I got a call from 3 users they cannot access Outlook for iOS and Teams anymore.

They got messages when they open Outlook like "Your organization is removing some data..." or "Your organization has removed some data... - Please log on with work or school account"

If the close the iOS App and open it again, Outlook says "one account found" if they click add account they get redirected to the MS-Authenticator App where they need to reenter a password.

Next they get error written in subject "User account ... does not exists"

(Windows PC / Outlook is working without any problem.)

If they close Outlook and reopen it again sometimes a screen is displayed "remove account - apps on this device are already managed" and twice the same email address.

If I remove the Outlook app and wait till Intune install it again automatically it works for a day.

Same behavior if I retire the phone from Intune and reenroll it. 

I enrolled one of my test devices with this user and there is no problem at all. Everything is working so far.

All devices I spoke are iOS devices with iOS 15.6.1 installed and enrolled with Intune Company Portal.

PS: The Tenant Name in Screenshot with error AADSTS50020 is not correct. This was the name of the old Tenant before migration. (2 Years ago)

I can not imagine why this error suddenly occurs - everything working fine the last 2 years...

I hope I explained it reasonably understandable

Attached some screenshot. (sorry but some text is in German)

Regards, 

Philip