Rekordbox can't find the Titles

 Hello,

ihave two extern Discs for the Music. I copy One Disc tobte Otter, so i have a Tour Disc und a Naster Disc. On the Tour Disc Rekordbox Play all Titles, Burg On the Masterdisc Rekordbox can't find the Titles.

I have a ITunes Mediathek, that Tuns On Booth Disc. The System i have is a Mac El Capitan.