Azure MFA breaks Office 365 and Teams authentication

Hi BoerelzZ,

Looking at your approximate challenge in this way, I don't immediately think of a problem with Credential Guard or with MDE. I would start troubleshooting on the authentication front. A few things you can check:

1. Make sure that Modern Authentication on your tenant is enabled. I assume it's already enabled, just to make sure (admin.microsoft.com --> Org settings --> Modern Authentication --> Check: enable Modern Authentication).

2. Check if the Office clients are supporting modern authentication (see this article: https://docs.microsoft.com/en-us/microsoft-365/enterprise/modern-auth-for-office-2013-and-2016?view=o365-worldwide)

3. Starting with build 16.0.7967, Microsoft 365 apps use Web Account Manager (WAM) for sign-in workflows on Windows builds that are later than 15000 (Windows 10, version 1703, build 15063.138). Please try the following registry change: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity change the DWORD value of DisableADALatopWAMOverride to 1.

If the problem persists, please run the troubleshooting tool Office Sign-in issues (Download link: https://support.microsoft.com/en-us/office/about-the-microsoft-support-and-recovery-assistant-e90bb691-c2a7-4697-a94f-88836856c72f) 

Looking forward to your reply.