The TV controls and the IR receiver for the remote control are connected to the mainboard so it may be a mainboard problem or a firmware problem. (The firmware is located on the mainboard anyway).
Make sure that there are no other remote control units e.g. Firestick remote etc in the same room (or remove their batteries), just to make sure that there is no interference to the TV operation being caused by them.
Does the TV power LED blink when you press other buttons on the remote control?
Try a power refresh and check if that resolves the problem.
Turn off the TV if on and then disconnect the power from the TV.
Press and hold the TV power button for 30 seconds and then release.
Reconnect the power to the TV and turn it on and check what works.
If still no good, turn off the TV if on and then disconnect the power from the TV. Remove the back cover from the TV and locate the button control board and also the IR receiver board. If they are located on the same board then the following will not work.
If they are located on different boards, carefully disconnect the cable from one of the boards, reconnect the power to the TV and turn on the TV by either the remote or the control button depending on which board you have disconnected and check. Study the connector first in case there are latches that need to be flipped up to release the cable or whether the cable can just be pulled straight out. If just pulling out, pull by the plug and not the wires.
Be safety aware when working in the back of the TV as there is exposed lethal AC voltage on the power board when the power is connected. Disconnect the power before doing anything in the back of the TV.