Unplug the Fire TV Stick from power
Remove the batteries from the remote
Wait 60 seconds
Reinsert the batteries
Press and hold the Left, Menu, and Back buttons together for 12 seconds
Release the buttons
Wait 5 seconds
Remove the batteries again
Plug the Fire TV Stick back in
Reinsert the batteries
Press and hold the Home button for 10 seconds to re-pair the remote
Repeat the pairing step if needed