Recently when I try to download an album from the iTunes store to my desktop iTunes Library, one or two of the songs will get "stuck" in downloading and never show up in my "Purchased" list. I can't include that song in the playlist I'm creating. I get this message: "Adding iCloud items to playlists will download a copy to your computer." I don't understand what's going on, and I don't like that I'm paying for music that I can't ever seem to access. What am I missing?