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. To locate and view the registry setting for Anonymous Authentication in the Outlook profile, follow these steps. This issue can occur if the Logon network security setting on the Security tab of the Microsoft Exchange dialog box is set to a value other than Anonymous Authentication. 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.

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

• Microsoft Outlook 2016 and some recent builds of Outlook 2013 are not affected by this issue.
• If this box is greyed out or disabled then you need to reset the Windows Credential Manager first.
• 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.
• In fact if you just turned on MFA and you were not using MFA before you usually end up having to rebuild the profile and clearing the credential manager.

You may have to rebuild/restore your outlook folder/files which is a pain. I’d do that one step at a Fix Outlook Not Opening After Windows Update time, forgoing the restore of the cached files. If this box is greyed out or disabled then you need to reset the Windows Credential Manager first. Or, any suggestion on how to fix this issue, even better.

Outlook stuck in an MFA loop

Close and open your web browser again and go into clear Outlook credentials manager SuiteFiles. You will most likely need to enter your Microsoft 365 credentials again so ensure you tick any box that says remember my credentials but it should now work for all future documents you open and not require your credentials. Upgrade to Microsoft Edge to take advantage of the latest features, security updates, and technical support. I regret that you are experiencing issues with your Microsoft installation.

Outlook 365 Password Prompt Issue on Windows Desktop

So not doing anything at all even seems to work. Which to me sounds modern authentication troubleshooting like the issue is service side, not client side. 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.