If the gas is on and working in the RV in general, and the battery is charged, it means there's something with the fridge that's preventing it from lighting. There are a few simple things to inspect:
1. There's often a manual shut-off valve that's a part of the fridge to check. On my Dometic, it's a bit that looks kind of like a large setscrew on the solenoid valve/burner assembly; turning it a quarter turn opens or closes it. Other makes or models may, of course, differ in details.
2. Check that the igniter is sparking properly, and that the gap for the electrodes looks reasonable.
3. Check that the burner assembly and general area is clean, free of debris, etc.
There are probably a few other simple checks. Those are the straightforward ones I'm aware of. I do know from direct personal experience that the fridge works a lot better with the gas shut-off valve open.