My Apple Remote is not working

The Apple Remote may have lost its linking with the Apple TV while without power. Try the three steps as outlined here (2nd half of the page): If your Apple TV remote isn’t working - Apple Support

Welcome to the Apple Community. 

There seem to be quite a few people who have issues after changing the battery in the Apple TV remote control. Is the battery inserted at the correct way round? Does it fit comfortably and make contact with all sets of contacts?