Apple tv remote control not working

"I tried all suggested solutions given by Apple and nothing worked."

Nonetheless, I suggest you refer to the last procedure in this Apple Support article and redo the pairing of your remote with the ATV4K unit.

If your Siri Remote or Apple TV Remote isn't working - Apple Support

This is a recurring problem. I followed the directions and the first few times (!!) it worked, but now it doesn’t. It simply will not control the volume any more. Apple needs to fix this - these devices are lemons.