Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Dear Kate,
To answer your first question, the "other account" is usually not visible anywhere in the interface. This error is caused by a cached credential or activation token left behind on the Mac, often from a previous user or an earlier sign in, so there is normally no account for you to find and delete manually.
On your second question, clearing the cached credential is generally all that is needed, then you sign in again with the correct account.
First, quit all Microsoft 365 apps. Then run Microsoft's License Removal Tool to clear the existing credentials from the Mac, restart, and sign in again with your correct account.
If the issue still persists, please search for the application name "Terminal" and run this command:
defaults write com.microsoft.Word ResetOneAuthCreds -bool YES
Replace Word with Excel, PowerPoint or Outlook based on the application you encountered this error message.
Since this is a work Mac, it may be managed by your organisation, in which case you might not have the rights to run the removal tool. If that is the case, or if the error continues after both steps, your IT administrator will need to take it from there. If you don't know who your IT administrator is, please refer to this article: How do I find my Microsoft 365 admin? - Microsoft Support
I hope this helps. Looking forward to your reply.
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