When you go "off grid" (without running the generator) then only part of the system will work, as shown here:
From your description, since you state that none of your 120VAC appliances are powered, you probably have this configuration.
In order for you to obtain 120VAC power to the 120VAC receptacles in this configuration, you must unplug the RV's main power cord from the RV park's shorepower pedestal and plug it into the generator's receptacle onboard your RV (usually located in the same compartment as the RV's main power cord). And of course, start the generator.