Will not crank

My running lights in the back were both out the truck was driving fine. I checked the fuse box under the hood by pulling all the fuses one by one and replacing them. After I did that I tried starting the truck and it will not crank. I checked the Battery, solenoid, and switching out the relays still will not crank. What could of happened after checking the fuses under the hood and all were fine to make the truck not crank when trying to start?