A new setting in iTunes 12.2.1 may automatically hide your library from any 3rd party apps like Dapper.
To check this:
- Open iTunes
- From the iTunes menu, select "Preferences"
- Click on the "Advanced" tab gear
- Make sure "Share Library XML with other Applications" is checked.
- 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.