Microsoft Copilot Desktop App: Work account login loops back – sign out of personal account to fix

If the Microsoft Copilot desktop app repeatedly redirects work-account sign-in to the browser and returns to “Sign in to Copilot”, check whether the browser is simultaneously signed into personal and work Microsoft accounts. Signing out of the personal account may allow the work-account desktop sign-in to complete.

I used Copilot to try to investigate my problem with the Desktop App - it would provide a mechanism for me to sign in, but it did so by launching a browser window, whilst the App itself returned to the login screen.  That wasn't what I wanted - I have too many browser tabs open already!  Copilot went a long way down the networking/proxy route, and then by chance I discovered this very much simpler solution in an identity-session conflict.

Symptoms:

• Copilot desktop app always loops back to showing “Sign in to Copilot” after completing the sign in.
• The Work authentication appears to be successful.
• The “Which Copilot experience are you looking for?” screen appears.
• Choosing the work experience opens copilot.cloud.microsoft in the browser.
• Desktop app remains signed out and loops back to "Sign in to Copilot".

Cause:

• The browser was simultaneously signed into personal and work Microsoft accounts.

Resolution:

• Signing out of the personal account allowed the desktop work-account login to succeed.