If the volume buttons on your Apple TV remote aren't working
Restart your remote. If that doesn't work, try adjusting your volume control settings.
Adjust volume control settings
Restart your Siri Remote or Apple TV Remote
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 your Apple TV turns off and on again.
Release the buttons. Then wait 10-15 seconds for a Remote Disconnected notification to appear on your TV screen.
Press any button on your remote. When the Remote Connected notification appears, you can use your remote.
Adjust volume control settings
Go to Settings on your Apple TV.
Select Remotes and Devices, then select Volume Control.
Select a different volume control setting and try your volume buttons again. For example, you can select TV via IR instead of Auto.
Get more help
Learn how to use a universal remote to control the volume your Apple TV.
Learn how to use the Apple TV Remote in Control Center on your iPhone or iPad.
If your remote still isn't working properly, you might need service. Get service.