Won't Start

I just bought a 2014 Challenger and it started fine but the previous owner was using the key fob inserted in the push button start ignition to start instead of the push button. I was told by the previous owner that the battery was dead in the key fob. I took the fob out of the ignition and put a new battery in the fob but when I tried using the push button start on the dash it gave a message saying "key fob damaged". So I removed the start button and reinserted the fob into the ignition. It worked just as before when I started it the next morning but when I went to start it that evening it would not start. I have tried for the past 2 days to figure out what happened but only have been able to get it to start 1 more time and it immediately died. Any advice on what has may have caused this and how do I fix it?