The USB flash drive must be in FAT32 format. If you download songs yourself, do not download lossless ones because they are not supported! To listen to lossless music, you have to buy a finished USB flash drive and go through special processing to make it compatible with the car. My 5 Series had various troubles before. First, the U disk format was wrong and the car couldn't read it. I changed several U disks but it still didn't work. In the end, I found out that it was because of the U disk format problem and I needed to replace it