AppleTV new remote doesn't seem to support motion in games

I have an AppleTV 4K and recently replaced its remote with the new model. Works well but today, the kids tried to use the game Dance Now (which they used with prior remote) and the game does not see the remote's motion sensor. (You are supposed to hold the remote and dance and it gives you points if you match the on-screen characters.) The remote otherwise works normally.

I unpaired and re-paired, no joy.

I tried to un-pair and then use the old remote but cannot get it to see the old remote at all (but that may just be because the battery is dead).

And unrelated (?), I am having a devil of a time each time I want to un-pair the remote. I click Remote in the Settings and it shows the serial number, firmware rev, and other info about the remote but no control to disconnect or un-pair -- until after many retries, there the buttons (disconnect and unpair) are! Then later, no controls again. So weird.

Any ideas what's going on? I'm pretty much out of ideas.