I had that happen to me the other week, I went out side and it showed both bottles empty.  So I took them out and low and behold one was full and the other was empty.  After some fiddling I found that I had a defective hose that takes gas from tank to regulator…..So I took it (hose) back to the dealer I bought the rv from and because it was within the warranty period they replaced it with a new hose…..Now gas comes out of both bottles….Some times it is the simple things that cause the most problems…..