Is this about the 2012/2013 model Apple TV box [A1427 or A1469]?
Identify your Apple TV model - Apple Support
Find your Apple TV model number - Apple Support
The legacy models Apple TV box need a different remote than the current models Apple TV box. Trying to update wouldn’t change that. The current remotes (Siri Remotes [A1513, A1962, A2540, or A2854]) are only compatible with the current models Apple TV box [A1625, A1842, A2169, A2737, and A2843].
Apple TV remote models and their compatibility - Apple Support
Apple TV (3rd generation) [A1427 or A1469] can be updated to system software version 7.9, but not any further.
Apple TV (3rd generation) [A1427 or A1469] needs the Apple Remote (aluminum) A1294.
Remotes need to be paired or linked to the box, else the box won’t accept the commands from the remote.
For the Apple Remote (aluminum) [A1294]: If your Apple TV remote isn't working - Apple Support - Internet Archive (2nd half of the page). Do both steps, the unlinking and then the linking — both using the buttons on the current remote.
For the Siri Remote [A1513, A1962, A2540, or A2854]: Pair the Siri Remote with Apple TV [A1625 or later] - Apple Support