The model number you listed didn't include the 'P' at the end which stands for pilot light. If it ended in 'E' it would have electronic ignition. I assume it is a 'P' model.
When you light the pilot light, does it stay lit without having to hold the button after 30 seconds? Is the flame mostly blue, with a little yellow? Is the flame surrounding the brass thermocouple tube? When you then allow the main gas to come on, is that when it blows out?
If the pilot light won't stay lit after you have released the button, that's an indication that you need a new thermocouple. If it stays lit then blows out with main gas flow, your combustion chamber might have an insect nest or spider web in it. Blow out the tube and try again. If the gas jet is clogged or dirty, it might need replacing. Don't try to 'ream' out the oriface, it can easily be damaged and fail, instead buy a new one the same size.
Your electric element might be burned out or just not connected. They usually have a separate switch inside the RV. Often an additional switch might be located in the WH compartment. The second switch is to turn off power when the tank is empty for winterizing. If you only had the one switch in the RV, it would be easy to accidentally turn on power on the empty tank and burn out the element very quickly.