I've followed Apple's suggested steps and it still isn't working. It won't let me connect or repair at the moment.
If your Apple TV remote isn't working - Apple Support
The Siri Remote should stay connected if charged and used as the single remote.
If the battery charge is below 20%, then you are advised to recharge. You’d get a screen notification. Charge for at least 30 mins if unsure.
If the connection is lost, then it should re-connect with one or two button clicks. (I find that the Menu/TV-Home buttons work better for this than the navigation pad.)
If the pairing is lost somehow, then you can pair again as described in the support document. There is no other method.
When pairing again, remove any other bluetooth devices from the vicinity for the least wireless interference.
IR (universal) remotes do not need pairing/linking with Apple TV 4K. My regular TV remote can be used with Apple TV for many daily functions. The old style Apple Remote (aluminum) can be used for many daily functions.
The software remote on iPhone or iPad may be used as an alternative remote. Set up the Apple TV Remote on your iPhone, iPad, or iPod touch - Apple Support
If the issue persists, then contact the Apple Support staff.