I have replaced everything except my transfer case and my 4x4 will not shift. on 1999 GMC Sierra 1500

My 4x4 is stuck in 4lo, replaced everything , what should I do next?

Asked by for the 1999 GMC Sierra 1500
What does a professional scanner say about this problem? Any codes for the transfer case?? It could actually be a mechanical malfunction inside of the case!
2 more answers , 3 more comments
check the control module for the tranfer case, fuses and or relays
Module is new fuses are good. Where is the relay?
where the actuators replaced, also known for faulty switch
Yes everything is new
First, turn on key, put your foot on the brake, then put the trans in neutral (auto) or push clutch pedal to floor (standard trans). Then push & hold 2hi switch until light stays on. If that doesn't do it, take it in to a pro to scan for codes.