Blown fuse
We found that the problem that prevented the truck from charging was a blown fuse for the on-board-charger. Before we just replaced the fuse, though, we needed to research the specifications for the charger and work with ZeroLabs to make sure the fuse was properly sized and there were no shorts or malfunctions that caused the fuse to blow.
In the end, we determined that the fuse was undersized for the potential current draw it could see. It probably worked when using certain chargers in the past, but it finally blew, likely when the vehicle was being charged after being completely discharged.