Rekordbox recognising itunes playlists but all files unavailable??

Hi,

For some strange reason after years of stability all of a sudden all of my tracks that I manage from itunes (using an external drive to store the itunes library) simply are not available in RB. The playlist and the track info is there, but no actual audio file. Can't work out how to fix it, tried everything that I can find online. Note - share XML is ticked in itunes. I have uninstalled and reinstalled Rekordbox. 

Any help massively appreciated, I have a gig in 3 days and panicking a bit!

Cheers,

Col