Exported Rekordbox tracks not showing up on Ddj-rx

Hi, I'm wondering if someone could help me please? I recently bought a second hand ddj rx unit and I'm having problems using the Rekordbox feature on it. My problem is that when I've exported tracks to a fat32 memory stick and put it in the RX unit they're not showing up in any of the files, tracks, artist etc they're all empty. I used the sync manager on a mac and ticked the little box for synchronisation or whatever and then checked the sticks in a cdj 900 and the tracks were all there and playing and I could go into all the folders etc but when I got home the files were empty. I've checked the stick on my pc and the contents folder is there with all the tracks in. It's driving me mad!! And I know the Rekordbox feature works because in some way I can't replicate or explain, I Rekordboxed a track on the app on my phone, moved all the Pioneer folders on my phone to a stick and when I put it in the RX the one track I'd done was there, with the cues I'd put in and it played. I then used the app on a load more tracks, moved the Pioneer files again and the tracks were showing up but not playing and I've not been able to do it again!!!! I hope I've explained it well enough for someone to help me out please, thank you