There are widespread reports that Microsoft AutoUpdate (MAU) version 4.22, which was released on 14 April 2020, doesn’t run correctly. If you have any of the Office 365 apps installed, you may find it trying to run repeatedly at frequent intervals, when it reports no updates are available, or it may simply get stuck running in the background.
You can download a fresh installer for MAU from this page. However, neither re-installing version 4.22 nor installing the previous version have altered its behaviour here.
Thanks to bucky @buckymsj for suggesting that those with a volume licence can simply uninstall MAU and run MacUpdater or use other solutions to obtain updates. In my case, my Office 365 subscription is paid through Apple’s App Store (I like the irony), although its updates are still delivered through MAU rather than using the regular App Store app, which has always struck me as being odd. There doesn’t seem to be any resolution for that situation. I have just forced the MAU app to quit (Command-Option-Escape) and left it to see what happens next.
In the normal cycle, Microsoft only updates MAU every month, so we may have to wait for resolution in late May. That may not be such a bad thing after all.
Microsoft has fixed this, in a new version of MAU which is available from the link above, and was released on 21 April. Thanks for the team at Microsoft for such as rapid response. Unfortunately, I can’t seem to get this fixed version to work normally either, but perhaps my system has just taken umbrage over updates for the moment.