There could be a number of things that are not allowing your RV Refrigerator to run on Propane. The first thing I would suggest you do is to perform some routine maintenance on the Fridge to see if that helps. If is does not you may have to have a Certified RV Technician take a look at it to diagnose and fix the problem.
Below is a video from RV Expert Mark Polk from RV Education 101, it gives you the proper steps to maintain your RV Refrigerator.
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