Hello @Hendrik Willing ,
Welcome to the MS Q&A forum.
My sincerely apologizes for the delayed response. As much as I’d love to help you and provide answer in German, my language skills are limited there.
From the translation I understand your colleagues are not able to login due to some issues with the MFA App.
I am providing below the list of troubleshooting steps which could help you resolve issues with the MFA Application and failed logins:
- Common problems with two-step verification for a work or school account.
- Troubleshoot Azure Multi-Factor Authentication issues.
- Manually add an account to the Microsoft Authenticator app.
- From AAD Admin side, check if account is not in the block list; force user to Re-register MFA and revoke existing MFA sessions.
Sincerely,
Olga O