MP3 Player Not Connecting

I have a basic MP3 player that I put a few songs on for my kids each summer before they go to camp. I can't get my mac to recognize the external player when I plug it in. I've tried two different mp3 players, tried different ports, tried to pull it up on the system report, etc. I am using the latest macbook pro. I was using an Intel Mac last summer and everything worked fine. Any known issues with the new mac?