A new setting in iTunes 12.2.1 may automatically hide your library from any 3rd party apps like Dapper.

To check this:

  1. Open iTunes
  2. From the iTunes menu, select "Preferences"
  3. Click on the "Advanced" tab gear
  4. Make sure "Share Library XML with other Applications" is checked.
  5. Quit iTunes

 Dapper 2.2 (to be released in mid August) and above will detect this and prompt you to change your iTunes sharing settings, but earlier versions will not.