I experience the issue myself as well, every once in a while. Tried CC cleaner to clean up registry and everything -- also keep in mind this modern authentication troubleshooting is a fairly recent reinstall of windows. I am unable to stay signed in to my work account on Teams, Outlook, Office365 for more than 5 minutes.

Outlook credential prompt loop

I disabled the Zoom and Adobe PDF plugins and it stopped prompting me immediately. My client’s Outlook will only continuously ask for the password diagnose Office activation conflicts after MFA is enforced and Office.com has been logged in. It would be nice if it distinguished between your password and the app password. You may have to rebuild/restore your outlook folder/files which is a pain. I’d do that one step at a time, forgoing the restore of the cached files. Not sure if it has to do with being an onmicrosoft.com account that has no domain assigned to it.

Loop of 'Sign in to your account'.

I had this exact issue on another machine, that after 2.5 hours on the phone with MS support (via Zoom), the solution was to uninstall MS Office 365 and reinstall it. Yeap, you describe it exactly and unfortunately we still don’t have an answer. Closed the window without entering anything and Outlook returned to ‘Connected to Exchange’. I created a new Outlook profile, and then the old one started working. I wonder if the compuer cached a new logon token or something that the old Outlook profile could use. Also, during the new profile creation, I was only prompted for a password and not for MFA.

Resetting the Windows Credential Manager:

When we opened the old, existing profile it didn’t ask for ANY authentication, it just started working. Office 2016 is already Modern Authentication aware so APP passwords are not required. Native IOS and Android Mail apps will require the APP password or users can use Outlook for IOS/Android which is Modern Auth aware. FYI outlook 2013 requires a registry setting to work with MA. Where I work, we have a new sandbox tenant to make tests before FixTechGuide email error solutions official deployment. I tried registering the account to my Outlook Desktop app and for some reason I am in a credential prompt loop that always asks for it anytime I input my password.

• Unfortunately when the problem occurs they’ve asked us to ring straight away but of course you can never get them instantly (we’ve just been given someone’s direct number now).
• Tried CC cleaner to clean up registry and everything -- also keep in mind this is a fairly recent reinstall of windows.
• I feel like this issue is getting progressively worse as the fix used to be clearing the credential manager or if it was bad uninstalling the entire Office Suite, clearing all traces and reinstalling and now we are seeing nothing helping it.
• This is now the 2nd machine that presents the same issue.
• There doesn’t appear to be any pattern to the issue occurring or the problem being limited to any specific computer or user.
• I disabled the Zoom and Adobe PDF plugins and it stopped prompting me immediately.
• Clear the Windows Credential manager or recreate the users Outlook profile.
• On the main machine where I have been using the suite, now my account is deactivated and if I try to authenticate, it looks like it works but then get the "Fix", "Authenticate", "Activate" or "Resolve" buttons, all of which do nothing.
• I have contacted my organization and everything looks alright from their end..

Changing Outlook Security Settings:

Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. Create your account and connect with a world of communities. I cannot find the phone number again to contact MS Office support (eventually they were helpful, but only after insisting they help!), I'm in the Netherlands so if someone has a phone number, I'd love to get it again.