that's pretty much what is playing in my head because I build motorcycles and they are super simple when it comes to a dead cylinder 90% of the time it's a bad connector on an ignition switch or a broke wire.
Problem is that's a big haystack to find a needle in..lol...I would hope someone had an idea of where some trouble spots could be in the harness

 

If you don't have a factory service manual for your truck yet, get one. Scope out the wiring diagrams, and see where the splices in the power feeds are. Those are going to be the likeliest spots for issues to develop.