Recently a button has stopped working via CEC on my Samsung TV (unfortunately it’s the back button). I’ve checked the debug logs, and running cec-client directly - the buttons don’t appear to register with libcec (the TV LED is flashing indicating that the button is being pressed, and it works in the Samsung menu’s, but not in libcec)
Almost certainly the issue is at the TV end rather than the Pi end.
I’d suggest disconnecting all HDMI devices from TV and unplugging it from the mains for a minute.
That encourages it to forget any state about the cec devices.
Connect the Pi, power the TV then the Pi and see if that starts working. You can then connect other devices (checking after each one that it hasn’t affected it).
You may also want to try disabling/enabling CEC on the TV (probably called Anynet+ in menus).
Looks like it was the remote batteries running low! Thanks anyway