Activation failed

Got it. Did a reinstall and all is well. 

Hi JonHunt,

Error code 0x0 is a bit unusual because it generally indicates the activation process didn't return a specific error, making it more of a generic activation failure than a licensing issue.

A few things I'd try:

• Sign out and back into Microsoft 365 from any Office application (Excel > Account or Help > Sign Out), then restart Excel.
• Open the Microsoft AutoUpdate app and make sure both Office and AutoUpdate are fully up to date.
• Confirm your Mac's date, time, and time zone are set automatically, as incorrect system time can interfere with license validation.
• If you're signed into multiple Microsoft accounts (personal, work, or school), make sure Excel is using the account that owns the active Microsoft 365 subscription.
• If the issue started after an update, try removing the Office license credentials from macOS Keychain Access (look for Microsoft Office or ADAL/MSAL entries), then sign in again to refresh the activation token.

Since you mentioned your desktop still shows an active subscription, the subscription itself is probably fine. This sounds more like a local activation cache or credential issue on the Mac.

This matches the Microsoft 365 for Mac licensing-certificate change that took effect on July 13, 2026. Older Office builds enter reduced-functionality mode, so they can open files but cannot edit or save. Excel 16.7.1 is well below the required current build.

In Excel, choose Help > Check for Updates, select Update All, and update to version 16.110 or later. If Office came from the Mac App Store, update it there instead. Quit and reopen all Office apps, then sign in with the account that owns the active subscription.

If AutoUpdate is missing or will not update, reinstall Microsoft AutoUpdate (or reinstall Microsoft 365 from your account) and try again. Only if activation still fails after updating, run Microsoft's Office License Removal Tool and reactivate.