But by mistake, I turned on MFA for the admin account, and then when I logged in again, it prompted me to use Microsoft Authenticator. The bad thing is this account was not registered with Microsoft Authenticator, so I couldn't see any codes Outlook Not Sending or Receiving Email in the authenticator. And there were no other login options, and I was stuck in a login loop. This is now the 2nd machine that presents the same issue. I have a valid MS 365 subscription that includes 5 device licenses. 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.

Outlook credential prompt loop

In the instances that this occurs the effected user is not new to MFA but has been running it for at least months. The problem appears to randomly affect users (I’ve had it affect myself once too), and the only solution appears to one of (or a combination of) the options in the OP. Out of 140 staff the problem seems to occur once every 2-3 weeks on average. In this case are you saying that there is a password prompt for the users credentials? Clear the Windows Credential manager or recreate the users Outlook profile. In fact if you just turned on MFA and you were not using MFA before you usually end up having to rebuild mailbox not updating on IMAP the profile and clearing the credential manager.

Loop of 'Sign in to your account'.

Which to me sounds like the issue is service side, not client side. A vast community of Microsoft Office365 users that are working together to support the product and others. I’ve seen this happen when the time and or date is wrong on the machine. It’s not caused by an out of sync MFA prompt as I have personally looked at a number of cases with the user as stepped through it. In each case the fix has either been one of the above items or a combination of them. There doesn’t appear to be any pattern to the issue occurring or the problem being limited to any specific computer or user.

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 Office 365 Sync Errors Fix 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.

• It would be nice if it distinguished between your password and the app password.
• I am unable to stay signed in to my work account on Teams, Outlook, Office365 for more than 5 minutes.
• We have been experiencing the exact same issue for months now.
• Create your account and connect with a world of communities.
• The user had Office 2015 and Office 2016 credentials and Teams credentials that we deleted.
• Today was the first time in about 2 months that I had the issue.
• We too have been seeing this more and more, all W10 on O365, although we use Okta as our MFA.
• Initially, this account didn't have MFA turned on, and I was able to log in.

Changing Outlook Security Settings:

If this box is greyed out or disabled then you need to reset the Windows Credential Manager first. @Microsoft, given the level of attention the community has given this issue, I hope you come up with an update soon. We have been experiencing the exact same issue for months now.