First, close the VirtualDJ LE software.
Make sure that the iTunes option to share the iTunes library XML with other applications is enabled. To do so:
- Open iTunes, go to Edit > Preferences (in macOS: iTunes -> Edit).
- Go to the Advanced tab.
- Make sure that the Share iTunes Library XML with other applications option is selected (i.e. ticked).
- Restart the DJ software.
- If your iTunes library is still not visible in the DJ software, reinstall the DJ software.