If you start with the brake petal depressed, you may have to do the crown shuffle (pick up your feet like your walking) a few times. The truck wants to see the switch in an opened and closed state before it will allow for drive functions.

If you go into the service menu the analyzer should show you if that switch is opened or closed. Make sure it switches between opened and closed when you pick you foot up. I think it is A2.1.2
0 = switch open
1 = switch closed