Hi James,
The issue may be caused by the damaged licensing files. So, I suggest you remove the following files if they exist and check if you can successfully activate Outlook for Mac:
1. ~/Library/Prefreences/ByHost/com.microsoft.office365.plist
(e.g. com.microsoft.Office365.000c292a3eed.plist)
2. ~/Library/Prefreences/ByHost/com.microsoft.longstringofrandomcharacters.plist
(e.g. com.microsoft.e0QyRjBFODBFLTM3NzYtNEFCOS1BMzVGLTc1Mjc2NzlCQUJDO.000c292a3eed.plist)
3. ~/Library/Application Support/Microsoft/Office/DRM/longstringofsamerandomcharacters (This is a hidden folder.)
If the issue persists, could you try resetting Outlook for Mac by following the steps below? Please note that the user profiles will be removed.
1. Quit Outlook for Mac.
2. Remove the following files:
~/Library/Preferences/com.microsoft.Outlook.plist
~/Library/Preferences/com.microsoft.Office365ServiceV2.plist
~/Library/Preferences/com.microsoft.Outlook.LSSharedFileList.plist
~/Library/Containers/com.microsoft.Outlook/
~/Library/Autosave Information/com.microsoft.Outlook.plist
~/Library/Containers/com.microsoft.Office365ServiceV2/
~/Library/Autosave Information/com.microsoft.Office365ServiceV2.plist
~/Library/Group Containers/UBF8T346G9.ms/
~/Library/Group Containers/UBF8T346G9.Office/
~/Library/Group Containers/UBF8T346G9.OfficeOsfWebHost/
3. Restart Outlook for Mac and reactivate it.
If it still repeatedly asks you to activate, for our further investigation, could you share the following information with us?
1. What’s the version of your operating system?
2. What’s the version of your Outlook for Mac? (e.g. 15.8)
3. Are there other versions of Office applications installed on your computer?
4. Could you tried clicking deactivate on the Office 365 software page and re-install Outlook for Mac?
Thanks for your time and effort on this issue. We’ll assist you further according to your situation.
Best regards,
LingYu Sun