If your Outlook suddenly starts prompting for a password after enabling multi-factor (mfa) or two factor authentication (2fa), you likely skipped a step.
Go here and download the Exchange Online PowerShell Module for MFA. You have to use Original Windows 10 Edge or Internet Explorer.
https://outlook.office365.com/ecp/
Click hybrid at the bottom of the left hand side navigation pane and then click the second configure button to download. Run the application.
Run these commands in the new powershell window:
Connect-EXOPSSession
get-organizationconfig | select oauth*
set-organizationconfig -OAuth2ClientProfileEnabled:$true
get-organizationconfig | select oauth*
