I feel like this issue is getting progressively worse as the fix used to be Outlook data file cannot be accessed 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. 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. Problem doesn’t just happen on PC’s connected to the internal network, but can happen when a laptop is remote and connected via external wifi or mobile hotspot. Today was the first time in about 2 months that I had the issue. It happened right before lunch, locked my machine, went out for lunch, came back, and logged in, this time successfully.

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 rebuild Outlook data file quickly the profile and clearing the credential manager.

Loop of 'Sign in to your account'.

We had the issue where Outlook 2016 kept prompting for a password for an Office 365 user whose laptop was connected to their Office 365 account using Windows 10 Pro. The repeated issue logging in started after I enabled the modern authentication in the Office 365 administration panel. The user could use the Windows mail and calendar apps but Outlook wouldn’t connect and kept prompting for a password. Checking the Account in Word showed the correct authentication and subscription.

Resetting the Windows Credential Manager:

If you are saying that they are getting multiple MFA prompts then this is an out of sync issue with the wrong code being used. We’ve got a support case opened with Microsoft on this one but it’s been FixTechGuide Windows update Outlook fix open for about 3 months. 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). To make a long story short we’ve since been asked to collect Outlook logs and install Fiddler to capture additional logging. Initially, this account didn't have MFA turned on, and I was able to log in.

• 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.
• Problem doesn’t just happen on PC’s connected to the internal network, but can happen when a laptop is remote and connected via external wifi or mobile hotspot.
• 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.
• Not sure if it has to do with being an onmicrosoft.com account that has no domain assigned to it.
• I have a valid MS 365 subscription that includes 5 device licenses.
• Hi, my office 365 account used to work with my desktop apps, I have confirmed with my admin system twice already that I have the appropriate license and everything is enabled but i keep getting stuck in this loop.
• Checking the Account in Word showed the correct authentication and subscription.

Changing Outlook Security Settings:

Hi, my office 365 account used to work with my desktop apps, I have confirmed with my admin system twice already that I have the appropriate license and everything is enabled but i keep getting stuck in this loop. We are looking at using conditional access policies where a user with a Domain joined PC is not prompted for MFA. Right now we have it set to prompt when a user is not on any of our corporate networks or they are using a mobile device. The 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.