I have this problem too, same build and everything! The keyboard illumination feature works fine on login, but the second I actually login the light turns off and there is no feature to turn the light back on (even the F5 and F6 keys don't register anything and it's not the sensor as all my lights are off). Also, the "illuminate Keyboard", feature from my system preferences is MISSING. It used to be there, but I downloaded Catalina and apparently my 'keyboard illumination' feature got removed or something. Please help.