Problems with HU recognizing USB drive
 

Hey guys I'm trying to play MP3 files through a USB drive on a 2013 BRZ Limited Head Unit. I've tried using two different USB sticks, one w/ 8GB and another with 1GB storage. They were both formatted in windows to fat32 and only have MP3 files on them. When I insert the USB drive, nothing happens. The 'USB' option on the head unit stays greyed out and non-selectable. Is there something special I have to do with the USB drive for the head unit to recognize it? I've also tried unplugging all connections on the rear of the head unit and that doesn't help either.