back-up lights…help

02 2500 manual gasser,
My back-up lights won't light at all. Bulbs are good, fuses are good but what else could I check to isolate the problem? I don't know if this is related but the cruise quit working some time ago.....but I don't know if it was the same time the back-up lights apparently failed. Any help or info would greatly be appreciated!
Author: whiteowl