My brother was issued a mandatory USB drive at school, but the drive doesn't mount on any Mac computer (it works fine on the PC). It is formatted as FAT32, which should be visible across platforms. It does not mount on any Mac computer and is not visible in Disc Utility. I tried re-formatting the USB as FAT32 (on the PC), but the issue remains. When I re-format the USB as FAT on the PC, the USB becomes visible on the Mac, but I cannot read/write from the drive. If I attempt to open a file, the USB immediate ejects/dismounts. I then tried formatting the USB via Disc Utility, but the option of MS DOS was already selected. I'm at a loss as I've never experienced a problem like this before. Any help would be greatly appreciated.