Apple Remote volume not working
My remote will not allow me to change volume
Question marked as
See: If the volume buttons on your Apple TV remote stop working - Apple Support
Else: The Siri Remote will send IR signals* for volume control to TVs or audio systems that have an IR receptor for such signals. It will used to most common signals for that by default. If your TV or audio system expects different signals for volume control, then Apple TV can learn that.
Settings﹥Remotes and Devices﹥Volume Control﹥Learn New Device…
(*Exception is receivers that support volume control through CEC.)