Computer "Authorization" issue

Hi, I recently purchased a number of new songs for the holidays. All purchases went through fine, and all songs show up in my iTunes library on my computer hard drive. One song however will not play. It always generates a "This computer is not authorized to play ______ would you like to authorize it now? I have authorized/deauthorized and re-authorized my computer numerous times to no avail. The only difference I notice now is that when I 'manage devices' in My Account, my computer is no longer listed, my iPod and iPad are, but my laptop no longer shows up. ALL of my music plays fine except for one recently purchase song. Any ideas?