Apple Remote has lost connection to your AppleTV.

Have you tried the IT Crowd "Have you tried turning it off and on again?"

https://www.youtube.com/watch?v=fU14GSc_mzA

You should be able to press and hold the TV/Control button for 5 seconds.

Let go of buttons within 5-10 seconds the remote should reboot and then should reconnect.

If it still does not work...

Hold the Menu and + volume button for 5 seconds close to the AppleTV.

It may ask you to put the remote on the AppleTV, Do this.