Your coach needs to know it has power from your onboard genny instead of the shore tie plug-in. Some have ATS (Auto Transfer Switch) that does this as soon as it senses power from the genny. Well, in 20-30 seconds after the genny starts actually. BUT BUT BUT Many coaches have an outlet, like the one on a campground pedestal, powered by the genny. You have to plug the shore tie cable into that outlet. Then start the genny and you should have power to let you run the A/C, recharge your House Battery from the Converter/Charger etc.
Take a look in the compartment where your shore tie cable is stored and see if there's a box with a socket in it.