I am by no means an electrics expert. Remember the engine starts on its own dedicated battery, and the coach guys should be completely independent. It's hard to tell from your pics which wires are going where, with most of them being RED, which is usually used only for POSITIVE or HOT wires. Your coach connections should be going to some sort of controller that routes juice to the lights, fans, fridge, water pump, and so on. But that should have nothing to do with the starting problem, per se. And I'm not sure which batteries are tied to the light on your dash, but if it reads "ALT", that's probably the engine battery.
A NO CRANK problem could be anywhere between the ignition key, the neutral safety switch, the starter, the battery, and few other spots that I can't think of right now.
If it cranks, but SLOWLY, that's usually BATTERY, less usually STARTER.
If it cranks like mad but doesn't fire, that's GAS or SPARK.
Sorry I couldn't be of more help.