I have power at fuse ,power at orange wire on brake pedal switch, when pedal is pressed white wire has power. No power at 15A fuse under dash. If I put a fused jumper on this fuse brake lights lite up. Changed brake switch also.

 

I changed the cab and everything was reinstalled into the new cab. The wire harness has to plugs that are identical . I had the wrong plug plugged into the brake pedal switch. I asked four different Chevy mechanics on just answer and not one of them was able to figure that out.