Apple TV does not sync w apple remote or iphone remote apps.

What is your model Apple TV box? Identify your Apple TV model - Apple Support

The official Apple software remote from the App Store was discontinued a bit over a year ago. The software remote from the App Store is/was still functional with iOS 14 or earlier. This app was compatible with Apple TV (2nd generation or later).

It was replaced with the software remote in Control Center. This rendition is compatible with Apple TV (3rd generation or later).

Set up the Apple TV Remote on your iPhone, iPad, or iPod touch - Apple Support

For originally intended functionality, you can buy a replacement remote.

For Apple TV (3rd generation or earlier): Buy the Apple Remote (aluminum) - Apple Store online

For Apple TV (4th generation or later): Buy the Siri Remote (2nd generation) - Apple Store online

It must be that the older generation apple tv doesn’t pair w newer remotes.

Indeed, the Siri Remotes are not compatible with 3rd generation or earlier. Identify your Apple TV remote - Apple Support