How do I fix remote pairing issues on Apple TV

What is your model remote?

Identify your Apple TV remote - Apple Support

What is your model Apple TV for which you wanted to pair?

Identify your Apple TV model - Apple Support

Find your Apple TV model number - Apple Support

What is its version system software?

The legacy models (A1469 or earlier) should use the legacy remote (A1294). The remote should be linked to the box to be functional.

Model A1625 or later should use the Siri Remote (any variant). Siri Remote (1st generation) is compatible with all versions tvOS (v9 or later). Siri Remote (2nd generation) is compatible with tvOS 14.5 or later. Siri Remote (3rd generation) is compatible with tvOS 15.4 or later. The current version is tvOS 18.3, and compatible with Apple TV model A1625 or later. The Siri Remote (any variant) should be paired with a box to be functional.

[tvOS] 13.4.8

Well, there’s the reason. Apple recommends keeping the system software on your devices up-to-date for best support, fixes, features, etc. Update your Apple TV - Apple Support

If updating fails then please contact Apple Support. The jump from 13.x to 18.x may be too much for the updater. To solve that, Apple may ask you to bring in the unit for updating using methods that may not be available to users at home.

The remote 2.: A2540 (This is for ATV HD 4gen. no problem, love it, but not 4K)

A2540 requires tvOS 14.5 or later, regardless of HD 4th gen or 4K.