General Electric Electric Wall Oven JRP15WP3WG Timer Repair

I am trying to help my brother with his wall oven. I am not 100% sure exactly what happened. He and his wife have a child on the way, and the wall oven was installed in their house when they moved in. The wiring on it was not good. There were wires coming from the conduit from the oven that had wire nuts going out to some romex for the house wiring just kind of laying all around under the cabinet. He thought he would fix the safety hazard, and put them in a junction box. The problem was that the wires were extended from the oven and not the right colors, can't say I blame him since there was no sign that they weren't the actual wires coming from the oven. He didn't inspect it until he had it all hooked back up and flipped the breaker for it, and then the breaker popped back out almost immediately. He inspected it and found out the true colors of the wires and he had wired the ground to the red wire, and red to the ground. Now that he has it wired correctly, it will not turn on at all.