Also, at the time, that user did not have MFA turned on. 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.

Additional resources

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. I checked my MS account info page, subscription is fine. 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.

Microsoft Office 365 Endless Authentication Loop Issue

• Native IOS and Android Mail apps will require the APP password or users can use Outlook for IOS/Android which is Modern Auth aware.
• There doesn’t appear to be any pattern to the issue occurring or the problem being limited to any specific computer or user.
• We are looking at using conditional access policies where a user with a Domain joined PC is not prompted for MFA.
• I checked my MS account info page, subscription is fine.
• When we opened the old, existing profile it didn’t ask for ANY authentication, it just started working.
• The user could use the Windows mail and calendar apps but Outlook wouldn’t connect and kept prompting for a password.

When we opened the old, existing profile it didn’t ask for ANY authentication, it just started working. Modifying the Outlook profile by using the "Profiles" registry path is not supported and may cause your Outlook profile to be in an unsupported state. FixTechGuide Office 365 troubleshooting Serious problems might occur if you modify the registry incorrectly. Before you access it, back up the registry for restoration in case problems occur. We are looking at using conditional access policies where a user with a Domain joined PC is not prompted for MFA.

Outlook stuck in an MFA loop

The Repair Outlook Profile Online user had Office 2015 and Office 2016 credentials and Teams credentials that we deleted. We checked with Word that the account was connected–it was and the we opened Outlook and it immediately connected. We too have been seeing this more and more, all W10 on O365, although we use Okta as our MFA. Have looked all over and people have all sorts of possible solutions, but nothing we found to resolve the issue and get a new issue daily and just keep going through until it eventually works. 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.

Outlook 365 Password Prompt Issue on Windows Desktop

Microsoft Outlook 2016 and some recent builds of Outlook 2013 are not affected by this issue. Those versions have been updated to prevent the problem that is described in the "Symptoms" section. These versions have the Logon network security setting disabled or removed from the Microsoft Exchange email account Outlook Stuck on Synchronizing Folders settings. It requests me to login to my microsoft account. I then approve the login with my authenticator app. Then i get rerouted to the login page again to repeat the process.