Are you using Office on Mac OS?
If so, have you added a shared mail box in Outlook? Or did you sign other accounts into Office?
- I suggest you run license removal tool first.
- Then delete all Keychain entries relating to Office.
- Besides, you may refer to the similar thread 'MacOS "Another account from your organisation is already signed in on this device"'.
But if you are using Office on iPad, it's recommended to post a new thread on Microsoft Answers Community. For Office issues on mobile devices are not supported on Q&A forum ~ Thanks for your understanding.
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