That's his old box and he said he replaced it with a new box. If something was mis-wired or a wire was fried at some point he can't see, the breaker immediately tripping can be happening, but that should be quite evident.Nice catch ! But I think he said he replaced it.. maybe he replaced that too.
But your exactly right no power at breaker -> = no power anywhere else.
Now I'm wondering if when he snaps the breaker on, it immediatly faults out.