backup lights not working

[Chevyboy1962]

Hey Gang,
I don't know wehre to really post this question, but I hope you guys could help me with it.
I finally got the backup lights hooked up, but the lights are not coming on. The switch i'm using is a 3 prong switch that lights up when it's turned on. The temporarally switch lights up, but not the backup lights. I can only think of a couple things that is causing them not to come on.

The first one is that the connections in the main tail wire harness (runs from cab to rear bumper), it has the extra wire for the backup lights. The second one is that I do not have the wires plugged in properly into the switch. Or three, the light switch itself is the wrong one to be using (the last 2 I dought).
What do you guys think?
Many thanks,
David