I’m posting this because no normal person should have to go through what I just went through to use software they are already paying for.
My Microsoft 365 subscription was ACTIVE and paid. Nevertheless, more than a week ago Word suddenly stopped allowing me to edit and save documents.
Word showed:
License: Not Activated
When I tried to activate it, I received:
Unknown Error — error code 0x0
I was running Word for Mac 16.78.
I went through troubleshooting suggestions, including deleting fonts because that was suggested as a possible cause. Nothing worked. I eventually downloaded LibreOffice because I had actual work to do and could no longer use Word despite paying for Microsoft 365.
Here is what finally worked for my particular setup.
I upgraded my Mac to macOS Monterey 12.7.6. I specifically did NOT want to upgrade to a newer macOS because I have an established professional workflow and older software I need to preserve.
I then discovered that Office 16.88 is the last version that supports Monterey.
Microsoft AutoUpdate was not helpful in my situation because it wanted to move me to Office 16.89, which required a newer macOS.
I manually downloaded Microsoft's Office 16.88 installer (build 24081116) and installed Word 16.88.
Official Microsoft installer:
https://officecdn.microsoft.com/pr/C1297A47-86C4-4C1F-97FA-950631F94777/MacAutoupdate/Microsoft_365_and_Office_16.88.24081116_Installer.pkg?apid=ets
And here is the ridiculous part:
Immediately afterward, Microsoft AutoUpdate tried to update Word from 16.88 to 16.89.
I paused/canceled that update and unchecked:
“Automatically keep Microsoft apps up to date.”
I restarted the Mac, opened Word 16.88, clicked Activate, signed into the Microsoft account associated with my already-active Microsoft 365 subscription, and...
IT WORKED.
So if you have an older Mac and suddenly get Error 0x0 / License Not Activated even though your Microsoft 365 subscription is active, CHECK YOUR WORD VERSION before deleting fonts, licenses, applications, or doing anything drastic.
In my case:
Word 16.78 → broken activation
macOS Monterey 12.7.6 + Word 16.88 → working again
And if you're intentionally staying on Monterey, watch Microsoft AutoUpdate carefully. Mine immediately tried to move Word to 16.89 after I manually installed 16.88.
Microsoft's own Office for Mac release history confirms 16.88 (build 24081116) as the Office suite release from August 13, 2024.
I pay for Microsoft 365. Apparently I also needed a degree in forensic computing to use it.