there is a shift interlock switch on the shifter. sometimes one or more of the wires break, in my case it was a yellow wire. you have to have the center console plugged in in order for the key to be released in case he has the center console disassembled.

 

I was going to have him check that switch. It isn’t disassembled, yet. With working on the Hummer at night and working in an Army motor pool during the day, he’ll be a mechanic in no time, ha ha.