You may have a loose gas fitting that is allowing the propane to escape when your fridge is not being used. This will allow air to enter the line and make lighting difficult. You can try bleeding the line before you initiate your gas start. I would check all your fittings and lines with soapy water to determine the integrity of your gas plumbing. Any bubbles will indicate a leak.

Gard

Our previous trailer had a 3.0 3 way (electric, propane, & 12v) fridge that was hard to start on propane. What I eventually found worked best was to open the propane bottle value about 5 to 10 minutes prior to trying to light the fridge, then hold the gas pilot light button in for at least 1 minute before trying to light the fridge, then push the striker button only once and then watch the gauge which in most cases went very slowly from the red (off) area to the green (on) area. Once the gauge reached the green area, then I would release the gas pilot light button, but not before. If I pushed the striker button more than once, it was actually blowing the pilot light out which I noticed when I had taken the outside cover off and had my wife pushing the striker button repeatedly inside. Good luck finding the trick on you unit.

I've also had the same starting issues with mine - thanks for all the tips.  One other thing you need to do is clean the pilot light area. 

Remove the outside cover and there is a small cover to the pilot light - using a toothbrush you have to put it inside that area and brush the blue cylinder, clearing off old debris.  You can also use a straw to blow the stuff away. 

A fellow camper had a service call on her fridge and she watched what the guy did - procedure above - he charged her $90 for the call.  She now does it herself and passed the info on to the rest of us.