If you have an older unit in your car....did you maybe put them on your flash drive as different types of files? I don't know a lot about these things but, I've learned by the mistakes I've made. I can burn tons of songs on a disk as a Data cd. They'll play in my car as it's newer formatted I guess (flash drive, etc). Will not play on older cd players. Recently I transferred songs as mp4s. I figured wth-sound better right? Somehow like 20 songs saved as videos. It took a week for me to figure out why. (Work, busy, blah blah) Just remove them from your flash drive & re do. Start fresh. Evidently there's something wrong or it would work. My guess it's the format, type of file???