I have a Sony soundbar that connects to a subwoofer where the TV HDMI cable and optical cable from TV connect. The Apple TV connects to the HDMI output from the subwoofer control box. I can't get the volume button on the Apple remote to control volume.
Verify the Volume Control settings on your Apple TV. If the Auto setting doesn’t work, then select one of the manual options.
If the audio systems uses a proprietary IR signal protocol that doesn’t match the default of the Siri Remote, then you can learn a new device.
Settings﹥Remotes and Devices﹥Volume Control﹥
Control your TV or receiver with your Apple TV Remote - Apple Support
Verify the Volume Control settings on your Apple TV. If the Auto setting doesn’t work, then select one of the manual options.
If the audio systems uses a proprietary IR signal protocol that doesn’t match the default of the Siri Remote, then you can learn a new device.
Settings﹥Remotes and Devices﹥Volume Control﹥
Control your TV or receiver with your Apple TV Remote - Apple Support
Remote volume button
