Your TCL remote is probably an IR (infrared) remote and doesn't have to be paired. I assume it doesn't have a microphone button which would make it a voice remote which would have to be paired. Only remotes that have to be paired show up in the TV's settings.
Remote buttons do wear out. If you mash the power button really hard does it work? You can verify whether IR remotes are working by pointing them at a digital camera like the one in your phone. When you press a button on the remote you should see a flash coming from the remote on the camera's screen. Try a few buttons and then the power button and check if you see anything.
Roku has a relatively new simple remote for TVs if you need to replace yours:
Roku TV Remote | Replacement Remote For Roku TV | Roku
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