We've seen several Mac users running Outlook who have gotten activation failures this morning. Apparently there's an issue on Microsoft's end. In the meantime, we've found that having the user quit all Office apps, then going in the Office 365 Portal and deactivating their Office install on that computer, then having them re-open Outlook resolves the issue.
We had several people reporting this issue as well. I deleted com.microsoft.adalcache from user's keychain. Re-opened Outlook, promoted to activate again. They were able to activate without any issue.
The issue was resolved by Microsoft this morning. Nothing you need to do outside of telling your users to quit the apps and relaunch them. Maybe they'll need to re-activate.
When we see activation issues, we sometimes run the Microsoft License Reset Tool: https://go.microsoft.com/fwlink/?linkid=849815 But can see that upgrades as of now do not need this and are working.
