Cannot activate Word Suite 2021, given error code 0x0, on my iMac

Question

I own a perpetual license for Office Home & Student 2021 for Mac, listed in my Microsoft account, added July 9, 2022. I use Office version 16.66.1 on MacOS Catalina 10.15.8. It's been working fine for years now until the last few days when I cannot access my Office suite, instead given "License: Not Activated" message. [I can only access my documents in view-only form.] I ran the Microsoft License Removal Tool and restarted my Mac. When I then signed in with my account, Microsoft accepts my email and password but then returns the same message previously received: "Unknown error 0x0" and Office remains unactivated. Please note I CANNOT UPGRADE macOS because my late-2013 iMac only supports Catalina.

Answer 1

If your macOS is below 12, Office products will now enter reduced functionality mode. In other words, the OS is too old to receive the licensing update the Office now requires. Sorry.

This is an update that occured on July 13th and Microsoft shared it here: https://support.microsoft.com/office/update-microsoft-365-or-office-on-your-macos-or-ios-device-f418ae5d-bb5f-4078-b3d9-9340f5dd084e?apid=ets

If your device cannot update its OS to at least 12, your options will be: Use the web version or an alternative like LibreOffice. Installing an older version unfortunately will not help.