Before trying to light the propane, always pre-warm your fridge apparatus by
turning it on the 12 volt setting for at least 1/2 hour. Otherwise it just
won't start. That's my experience, anyway--it drove me nuts before I
discovered this.

Of course, there could be something else wrong too. But even if the fridge
works  perfectly, it won't start on propane without doing this.

I found that mine works a lot better after blowing compressed air through
the vent hole below the door and through the flue pipes on the outside. I
also blew electronic parts cleaner through the hole beneath the door (with
flame off!) and that seemed to help with an issue of the fridge not staying
lit for very long. The combination of a blast of cleaner and then compressed
air, several times, made a huge difference in the way it runs.