tvOS 17 brought some new features but it also made my volume buttons stop working on my AppleTV remote.
I exhausted all of the things I knew how to do to fix this, and then after a quick google search apparently this just requires a remote restart. That process is documented here.
tl;dr:
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.