Chevygirl03

I have a 2003 Chevy Silverado 1500hd, I have changed the t-case, the actuator, the dash buttons, the TCCM, the encoder motor, cleaned the cables on the frame, checked the wires from tcase to under the hood, and for some reason the lights on the 4wd buttons won’t work, they light up when you turn the key on but once the motor starts the lights go out and stay out. I can’t get the tcase to engage, the reverse only operates when the motor is hot, I’m at a loss, help me please.