Propex x3 heater

While I am not familiar with this heater, quick question?
Is the gas switched on? Usually in a mh after the gas pipe leaves the regulator in the gas locker, it passes onto a bank of lever valves. Theses lever valves are located in a wardrobe or under a bench seat beside the locker. Each lever valve is for each individual appliances, gas hob,oven,and etc. Check that all are switched on and that each one feels the same. Your heater valve could be turned off, or the lever could be not spinning the valve on.
Alternatively a photo of the heater,its switch or its manual would help to find an opinion here.
Malcolm
Ps some heaters require the outside plastic cover over the exhaust to be removed for it to function.

Not sure where you are as it's not in your profile, but there is a guy in Doagh who works in Eberspachers (sp?). He might be able to help.