Brake "safety" switch Question

I believe the light is on for a reason because the brakes dont work worth a darn. I can get the front to lock (barely) on my dirt driveway, but I cant get the rears to lock at all. Again everything in this system is brand new (including this second new unit from classic industries P/N MD2268. When I ran a junk yard unit between the first and second new valves from C.I. it worked great, but the junk yard valve was a leaker.
Is there some special procedure I missed during install?