Windows 11 Microsoft Account authentication fails system-wide – WAM/Sign-in issue

Hello,

I am experiencing a system-wide Microsoft account authentication/sign-in problem on Windows 11 25H2. Microsoft Support has already assisted me with extensive troubleshooting and recommended that I report the issue here because the problem appears to be related to the Microsoft account authentication/sign-in process rather than to a specific Windows user profile.

Main issue

I am currently using a local Windows account. When I go to Settings > Accounts > Your info > Sign in with a Microsoft account instead, the process eventually asks me to authenticate my existing local Windows account.

The password for my local account is definitely correct and works normally on the Windows sign-in screen. However, the same password is rejected during the Microsoft account linking/conversion process.

The problem is not limited to my Windows user profile.

To test this, I created a completely new local Windows test account. The exact same problem occurs there as well: the local password works for signing in to Windows, but is rejected when attempting to link/convert the local account to a Microsoft account.

This strongly suggests that the issue is system-wide rather than caused by corruption of my individual Windows user profile.

Additional Microsoft authentication issue

I also tried to submit this problem through the Windows Feedback Hub. During the submission process, Windows Security asks me to verify my identity for my Microsoft account using my Windows Hello PIN.

My correct Windows Hello PIN is rejected with the message that the PIN is incorrect. Therefore, I cannot submit the report through the Feedback Hub.

At the same time, I can successfully sign in to my Microsoft account through a web browser. In fact, I was able to sign in to the Microsoft Tech Community through the browser in order to submit this report.

Additional symptoms that have now appeared

The problem is no longer limited to linking my Microsoft account to Windows:

• Outlook is no longer reliably receiving new emails.
• Microsoft Word can no longer save documents.
• Feedback Hub cannot authenticate my Microsoft account because the correct Windows Hello PIN is rejected.
• Microsoft account authentication through the web browser continues to work normally.

These additional symptoms make me suspect that there may be a common problem with Microsoft account authentication, WAM (Web Account Manager), the account broker, or another Windows authentication component.

Troubleshooting already performed

Extensive troubleshooting has already been carried out:

• The problem was reproduced with a newly created local Windows test account.
• The local account password was verified and works correctly at the Windows sign-in screen.
• SFC was run and did not identify an unresolved system-file corruption problem.
• DISM was run and the component store was repaired/checked.
• A Windows 11 repair installation was already performed. The problem remained afterward.
• Relevant Microsoft account/authentication components and services were checked.
• Microsoft Account Sign-in Assistant, WAM-related components, Account Control/Credential Provider-related components and associated services were checked and appear to be present/running.
• Credential-related services, including Credential Manager/Vault-related components and TokenBroker, were checked.
• The issue persists across multiple local Windows accounts.

Microsoft Support has therefore concluded that this does not appear to be a simple user-profile corruption issue and may instead involve the Microsoft account linking/authentication pipeline.

Current situation

Windows 11 25H2 is otherwise running, and my Microsoft account itself is accessible through the browser. However, Microsoft account authentication within Windows appears to fail in several places.

I would therefore appreciate assistance in determining whether this is a WAM/account broker/Microsoft account authentication issue and how the affected Windows authentication components can be repaired or reset without reinstalling Windows from scratch.

Please let me know if diagnostic logs, event logs, correlation IDs, or any other information would be useful. I can provide additional diagnostic information if required.

Thank you.