A constant appearing message in Word and Excel about to “Check for updates” triggered me to start updating Microsoft Office on my Mac. Normally it starts Microsoft AutoUpdate (MAU) which searches for Office updates. Now it did open the tool, but it looked like it failed updating itself and got stuck in the “Installing” state before it could update Office.
This was really annoying, because Office apps kept notifying me of available updates after every restart of one of the Office apps. So, time to fix this. The MAU version that had the issues was v4.39 (September 14, 2021).
While searching for a solution on the Microsoft Office forum, I found a post that mentioned to check the AutoUpdate file permissions in the LauchAgents and LaunchDeamons system folder and reload it. The permissions of the AutoUpdate files should be root:wheel according to the post.
hostname:~ user$ sudo chown root:wheel /Library/LaunchDaemons/com.microsoft.update.agent.plist hostname:~ user$ sudo chown root:wheel /Library/LaunchAgents/com.microsoft.autoupdate.helper.plist hostname:~ user$ sudo launchctl stop /Library/LaunchAgents/com.microsoft.update.agent.plist hostname:~ user$ sudo launchctl unload -w /Library/LaunchAgents/com.microsoft.update.agent.plist hostname:~ user$ sudo launchctl load -w /Library/LaunchAgents/com.microsoft.update.agent.plist
In contrary to others on the forum, it did not fix the issue for me. So I went ahead and found the release notes of Microsoft AutoUpdate and found that it can be downloaded and installed separately from Office itself. The latest version can be found here. The release notes mentioned that Microsoft switched to a new CDN in the v4.40 release, which triggered me to try updating it manually before trying something else.
So I downloaded and installed the latest v4.42 version (December 14, 2021). Voila, this instantly fixed the issue and updates for Office were shown instantly!
Hopefully this helps you fixing your AutoUpdate issue.