How To Reset the Apple TV Remote

1. Press and hold the TV/Control Center button  and the Volume Down button  at the same time. Hold the buttons down for about 5 seconds, or until the status light on Apple TV turns off then turns on again.  
2. Release the buttons, then wait 5–10 seconds. A Connection Lost notification will appear on your TV screen. 
3. After your remote restarts, a Connected notification will appear on your TV screen. 

My 2021 Apple TV 4K with the new remote stopped controlling the volume on my Denon AVR-S730H A/V Receiver. The Apple TV 4K was running the latest tvOS. I rebooted the device several times and unplugged it and left it overnight. I deleted and “Leaned New Device” in the Settings–>Remotes and Devices–>Home Theater Control–>Volume Control area several times. My receiver did not respond to the Apple TV remote.

When I reset the Apple TV remote using the method listed above, the remote started controlling the volume on my receiver perfectly. It took me a long time to find this fix so it is posted here.