Apple TV remote doesn’t control volume
My third generation Apple TV remote ceased controlling volume on my Vizio tv.
I tried all the procedures recommended by Apple, but none worked
Apple TV HD, tvOS 18
Did you try this one?
If the volume buttons on your Apple TV remote aren't working - Apple Support
For Apple TV settings, verify that the volume control setting is using “TV via IR”.
Settings﹥Remotes and Devices﹥Volume Control﹥…