Microsoft 365 and Office

This usually happens for one of these reasons on Mac:

1. The wrong Office build is installed If Office apps were downloaded from the Mac App Store, a one-time license such as Office Home and Student 2021 is not compatible with those apps. In that case, Office shows a yellow message bar and goes into reduced functionality mode.
2. The license needs to be refreshed or reactivated A one-time license can sometimes stop being recognized and Office becomes read-only until the license is refreshed or Office is reinstalled from the correct source.
3. Office activated with the wrong license If multiple licenses were used on the Mac, old license files can cause Office to use the wrong activation state.

What to do:

1. Check whether Excel came from the Mac App Store If it did, uninstall that version and reinstall Office from the Microsoft account Services & subscriptions page so it matches the Office Home and Student 2021 license.
2. Try refreshing the license in an Office app In Word for Mac, go to Word > About Microsoft Word > More Info > Refresh License. Then sign in if prompted.
3. If the problem continues, remove old Office license files and reactivate Use the License Removal Tool / Remove Office license files on a Mac, then reactivate Office.
4. If needed, reinstall Office from the Microsoft account If the license still is not recognized, reinstall from the Services & subscriptions page for the Microsoft account that owns Office 2021.
5. If Office was recently deactivated or signed out Sign back in with the account associated with the Office license.

Expected result:

• If the correct Microsoft-downloaded Office 2021 build is installed and the license is recognized, Excel should return to normal editing mode.
• If the Mac App Store build is installed, the one-time Office 2021 license will continue to show activation prompts until the Microsoft-downloaded build is installed.

References:

• Microsoft Office activation and the Mac App Store
• Reactivate Microsoft 365 or Office
• What to try if you can't install or activate Office for Mac
• Microsoft Office stopped letting me edit. Requires Office 365 to edit - Microsoft Q&A
• I bought & installed Office 2021 for Mac 3-4 years ago and yesterday it wrongly thought I had just downloaded 365 and has blocked me from using Office - Microsoft Q&A
• Message to "Activate 365 to create and edit" - don't understand WHY??? How to fix please. - Microsoft Q&A