RV fridges take a LONG time to cool , 24 hrs minimum , I start mine 48 hrs before I put food in.
The fault light is an indicator that the water heater failed to light in three tries , so the control board shut down .
Turn the water heater off, make sure the service valve at the propane tank is ON, note that opening the service valve too fast can trigger the safety " line burst " shut off built into the tank , that requires system back pressure to keep open. Turn the service valve off , then open it SLOWLY to re-set.
Light a stove top burner to insure propane is in the system , then restart the water heater.
EDIT: Do you have the owners manual for the fridge , maybe the manual can provide info on the switches , my older Dometic doesn't have those.