Office 365 (MAC) - Another account from your organization is already signed in on this computer

When you try to activate Microsoft 365 apps, you receive the following error message even though no other account is in use:

Sorry, another account from your organization is already signed in on this computer

Note: This error is expected if you're already signed in by using another Microsoft 365 account from the same tenant.

If this error occurs when only one account is used, follow the steps that are appropriate for your device:

• For Mac devices, follow these steps:

  1. Close all Microsoft 365 apps.

  2. Open Terminal, and then run the following command:

     defaults write com.microsoft.Word ResetOneAuthCreds -bool YES

  3. Open the Microsoft Word app and continue with the activation steps.

  4. If the issue persists, try the steps in Can't sign in to an Office 2016 for Mac app.

https://learn.microsoft.com/en-us/office/troubleshoot/activation/another-account-already-signed-in?source=recommendations