Suburban Water Heater won't light

Have done all kinds of searches but am still confused. I have a Suburban SW6DE heater that will not light on propane. It was fine when stored a year ago but now does not work at all other than on shorepower after replacing the electric element which was fried. We have not used the heater on 110 V since buying the unit used 3 years ago. And I am assuming the element has always been toast. So the question I have is: How do I determine whether the problem lies with the control panel or gas valve. I don't want to order a replacement only to find I got the wrong thing. This is what happens: When I turn the heater switch on it tries to light for the 3 programmed attempts and then locks out. There is spark at the igniter but I can detect no propane odour at all. The tube from the valve to the heater seems OK and I did use a small diameter brass wire to poke into the gas oriface. I have recycled the off on switch several times in a row to make sure that the line would be charged with propane. The stove and furnace both light.Lots of propane. I used a mutimeter and checked all four connections to the valve while trying to fire the unit. There is activity at all connectors but I cannot give definite values as the readings fluctuate so widely. Any and all advice appreciated. The nearest dealer is quite a piece away. I phoned them but they do not stock the valve and would have to order one for me. Thanx