Copilot login error 4vt9f

Question

Hello,

I have 1 user who we are trying to setup with M365 Copilot. He is able to access the web app and can use Copilot just fine from inside the various Office apps. So we took it to the next step and installed the M365 Copilot App on his Windows 11 Active Directory joined laptop. Immediately after installing the app it asks him to login, odd since other office apps are logged in but ok). When he is brought to the login page he is shown a M365 username he no longer uses (it was something we used prior to syncing Active Directory to M365). He removes that username and enters his current one and password, and it blinks a bunch of times then displays this error:

When he clicks close it just brings him back to the login window for Copilot.

We have already checked the windows Credential Manager and removed any Office relate logins, also removed the old M365 account from Settings > Account and rebooted. No change. We also uninstalled the Copilot app and reinstalled it. Still no change.

Lots of suggestions to repair/reinstall office but Office isn't the issue here so I don't think that makes sense. What else could it be?

Answer 1

Dear @Joe Sherman,

Thank you for posting your question in the Microsoft Q&A forum.

In this case, you can also try to sign out of all Microsoft apps > Press Win + R > Type: %LOCALAPPDATA%\Microsoft > Enter > Navigate to each folder and delete all contents. After that restart the device. For reference:

C:\Users\%username%\AppData\Local\Microsoft\OneAuth\blobs
C:\Users\%username%\AppData\Local\Microsoft\OneAuth\accounts
C:\Users\%username%\AppData\Local\Microsoft\IdentityCache

If the issue still persists, maybe the local settings had affected the application. Thus, I would like you to check whether the issue is related to your user profile. In this situation, I suggest you Create a new user account under your Windows. See if it still alerts you with the same error message. It is worth trying because it will help you narrow down whether the issue is caused by a specific corrupted user profile.

Note: Please understand that as a forum moderator, my role is to provide general guidance and troubleshooting support. I don’t have access to internal systems or backend tools, and I appreciate your understanding of these limits.

I hope the information shared helps point you in the right direction. Please try the steps above and let me know if they work. If not, we can continue working together to narrow this down.

The first response may not always resolve the issue right away, but with your help and more details, we can work toward a solution.

Thank you for your patience and understanding. I'm looking forward for your reply.

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