In article , says...

When I start Windows, I get a popup box

Windows Defender

(i) This program is turned off

If you are using another program that checks for harmful or
unwanted
software, use the Action Center to check that program's status.


If I open the Action Center, I just see two (orange) sections: one
telling me "Windows Update is set to check with you before downloading
and installing updates.", which I have no intention of changing!, and
one telling me "Your files are not being backed up.", which just means I
don't have an _automatic_ backup in place.

There is no mention of AVG at all.

I'm sure I've seen Action Center acknowledge, and reflect the settings
of, AVG before now. (AVG's icon is in the tray, _without_ a yellow
triangle on it; if I click on it, it comes up and tells me "You have
basic protection", and "Virus definition: 3 hours ago".

So how do I remind Action Center that I have a working and up-to-date
copy of AVG? (Do I have to do something from within AVG?)

I get the same. I think it's something to do with MS and an update. When
it sees another AV program running Defender shuts down on purpose but
the Action Center doesn't interpret that correctly. I dismiss it and
think no more about it.