Go into the iTunes preferences, click the Advanced icon at the top and check that this box is ticked:

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I recently upgraded to El Capitan from my original snow leopard software and now I can't import any tracks! I get an error "the iTunes xml file specified is unable to be read properly. How do I fix this?? I am running the latest rekordbox software and iTunes 12.4.2.4
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Go into the iTunes preferences, click the Advanced icon at the top and check that this box is ticked:

Tried that already and didn't work. I was able to find a solution for now by dragging tracks from iTunes into rekorbox and was able to import them.