I have added the file .is_audio_player and still no luck. Any Suggestions?
In Ubuntu 12.04, when I connect mp3 player, the home folder opens and I can see files that I have added to the player since I started using Ubuntu, however any music/podcasts/audiobooks that I put on the player when I was using Windows do not show at all. They do not show in Rhythmbox either. Ubuntu will recognize the mp3 player in msc but not in mtp.
51 Answer
I was having the same problem with files not appearing when my device was connected to my PC. (Sansa 240)
I initially attempted to select "Show hidden files" in my File Explorer options setting, but that was already selected.
Further Googling then lead me to the Sandisk website where I learned about the USB mode (connectivity) problem. It says that I should switch to the MSC mode on my device, then connect to my PC. When I checked, MSC was already selected but there was another option called Auto Detect, which I selected. When I connected to my PC, my folder view instantly changed and I was finally able to see my music files (and delete unwanted ones). So it was not actually the MSC mode that I needed, but I learned that I had to "unselect" it in order to view my Sansa files on the PC. Go to Settings on your device, and there should be a USB setting you can adjust.
Try this option and see how it goes. Here is the link.