Defender red x in Taskbar- Actions needed- but what?

Hi, about 10 days or so ago I noticed the Defender tray icon had started to show a red x - 'Actions Needed'.


Clicking on that opens the background window, and clicking on 'View Antivirus Providers' which seems to offer the only apparent reason for the red x gives the foreground window, which has nothing to do with AV providers.

There's nothing untoward if I expand the dropdowns.
I use Avast and have SecureAplus (no real time scan) installed.

I feel I'm missing something obvious, but can't think what it is....

Any ideas? Thanks!

What happens, if you click on Device performance and health (in Defender home)?

You could try running perfmon /report(from cmd, or run, or even File Explorer address bar) and see if it gives you any clues.
and Cortana:

I've got that red cross once. The culprit was health department - one device wasn't properly installed. That's why I asked what shows Health icon.

All ok, thanks.

Unable to run perfmon
- either timeout or
The Data Collector Set or one of its dependencies is already in use.
- a common issue..

Fixed itself... I had an unexpected action centre notification about something it didn't like, cleaned it, and back to green is good again. :)