Have you brought the batteries back to the RV and installed them? And you still have no lights? And you tried again to shift the USE/STORE switch to USE? and no sound or lights still?
There is a 50 Amp DC Circuit Breaker in the battery compartment that may have tripped. It looks like:
It may be red instead of yellow. Push the button to trip it (if not already tripped) and push the flag back in to reset it. Then try the USE/STORE switch again (assuming your batteries are charged and properly connected).