The steps outlined below may resolve the issue you have with your song no playing:
Specific purchases from the iTunes Store don't play
- Try deauthorizing and reauthorizing your computer. Repeat the deauthorization and reauthorization process for any other iTunes Store accounts for which your computer is authorized.
- Double-click one of your affected iTunes Store files.
- Enter your account name and password in the resulting dialog.
- Click OK.
After you've deauthorized and reauthorized your computer, open iTunes, select your iPod, and choose Sync iPodfrom the File menu. If that doesn't resolve the issue, try restoring your iPod.
After you've restored your iPod, open iTunes, select your iPod, and choose Sync iPod from the File menu. If that doesn't resolve the issue, try recreating your iTunes library.
After you've recreated your iTunes library, open iTunes, select your iPod, and choose Update iPod from the Filemenu.
If none of the above steps resolved your issue, there may be an issue with the music files. If you have a backup of the affected song files, delete the files from your iTunes library and then add them back in from your backup. If you haven't been keeping a backup of your purchased music, you can find out how to do this here.
If the affected files came from an audio CD, try importing them into iTunes again from the disc. After you've replaced the affected files with copies from your backup or CD import, open iTunes, select your iPod, and chooseUpdate iPod from the File menu.
I hope this information helps ....