Fix: iTunes Stuck or Not Copying/Syncing Music to iPhone
Is iTunes refusing to copy music to your iPhone or iOS device? When you drag a song(s) into an iPhone playlist in iTunes, you see the grey circle not move. You are forced to delete the uncopied grey songs and re-add them, but still sometimes the copy does not work. In addition, quitting iTunes and rebooting your iPhone do not fix the iTunes music copy issue. You will need to clear out your iTunes cache in order for copies to work again.
1. Ensure iTunes is not open. In Mac OS X finder, open the Go menu item and select Go To Folder…
2. Type the following path.
3. You can delete all the files in this folder.
4. Log off your account or reboot your Mac.
5. Once you are logged back into your computer, open iTunes and connect your iPhone. Try to copy music again. It should work.