Originally Posted by Rayco
if the sheaf of literature in the Jayco bag is correct, it's a Dometic
That means it's an Atwood.
If the electric element isn't working, and the gas burner isn't lighting, that points to the control board. Is the DSI fault LED lit? If it is, it may be the thermocouple.
If it's not, the control board may not be getting power, it may have failed, or perhaps there is wiring damage between the control switches and the water heater.
You need a multimeter to do this, but I highly recommend measuring the low-voltage connections to the WH control board to make sure 12v is getting to it and to make sure that the gas/electric switch connections have voltage when turned on too.