The rear dome light on my truck (Ford (YF1Z-13776-AA) has only one functioning switch. (The little gray switches) the one on the driver side is not working. I but a new bulb in so I cant be that. Could it be a fuse? Or is there a common fail on this part. I know it's something small but I am restoring this truck back to it's former glory.

 

i would be super surprised if that assembly had multiple fuses. Depending on the bulb type if you've replaced it and flipped it around and checked it that way too then my assumption would be the switch itself has failed.