I assume that fridge can be run on 120 v electrical as well as propane, and that it might run on 12 v too.
And most certainly I wouldn't try to run it at all unless the rig was level.
I get the error message, too, if I try to run it on propane when propane is unavailable, either because it isn't turned on, or because the propane lines have not yet been purged of air. The fridge will try to light the burner 3 times, and if it fails to light, you get an error code.
There are a couple things you might do. One is to make sure that it is set to 120 v electrical mode. Another is to turn on range top burner and get the lines purged that far before trying the fridge. You can also shut the fridge off after getting the error, give it 30 seconds or so to reset itself, and try again. On occasion, I've had to do THAT two or three times before success.