Stereo/surround sound

I am having issues with my stereo system. I loaded a couple of USB drives with music from my library to play in the Cruiser's stereo system. After several attempts I got it to work, mostly. Some song played and others said "this file type not recognized". All files are mp3 format and play fine on other devices. So after listening to one artist for a awhile we decided to change. Removed the USB drive an inserted a different one. Not recognized file type appears on all of these. Oh well could be worse. Put the original drive back in and now it won't recognize those songs.
Totally confused. Read the manuals a couple of times and it doesn't answer my questions.
Need help!

Hi,
Best way to play mp3’s is to create a separate file folder, load all music you want to listen to and the order you want it to play and then when file comes up on your screen select it and you should be good to go.
We use a seagate 1TB external hard drive and watch all our movies (500 +) and have 2000+ songs on a device smaller than a dvd.
Enjoy
Greg and Jan