When you are done closing all other faucets and the cold water still running then check your bypass unit.
Camper gas hot water heater not working.
If you are utilizing a tankless water heater and its gas powered then you should check to see if there are any damaged parts inside the casing of the water heater.
If you have more than one faucet open at the same time cold water will flow from one and hot from the other.
Rv hot water heaters are small and cannot handle having two faucets open at the same allowing for hot water to flow to both.
Next use a voltage meter to check the input to the heater which should be at least 10 5 volts.
Light the stovetop burner and look for a steady flow with a solid flame.
Check for any corroded or damaged working parts.
The camper water heater is designed to function in a way that only one faucet can produce hot or warm water.
If this does not fix the issues additional rv water heater troubleshooting will be needed.
If more than one is open then you re creating a room for cold water to mix the hot water.
Check for open faucets.
First things first you should check that gas is coming through to your appliances.