Can you lock and unlock the doors using the buttons on the center consul? Have you done the reprogramming procedure for the key fob after ensuring batteries were good? I am not an expert by any means, but if you have a key that starts the car you shouldn’t have to do anything with the SKREM. rather than the remotes themselves. Even if the second key doesn’t start the car you should be able two pair it to use the keyless entry function if it had previously been paired with that car . It is unusual that you would not be able two pair and use either of the keys. Perhaps the signal is being received but the air pump or whatever in the trunk area isn’t getting the pressure or signal to the lock mechanisms. If the console button works you could rule that out. It is odd that the second key would not start the car unless the transponder chip was removed or lost when changing the shell. I am wondering if the locking and unlocking functions could be related to the body controlModule