I just recently bought an EP from Florrie off of iTunes, and I can play every song except Summer Nights. Every time that I try to play it I get a pop-up claiming that my laptop needs to be authorized before I can play the song.
That suggests that particular track is damaged.
If your country's iTunes Store allows you to redownload purchased tracks, I'd delete your current copy of the track and try redownloading a fresh one. See the following document for instructions:
Downloading past purchases from the App Store, iBookstore, and iTunes Store
Otherwise, I'd report the problem to the iTunes Store.
Log in to the Store. Click on "Account" in your Quick Links. When you're in your Account information screen, go down to Purchase History and click "See all".
Find the item that is not playing properly. If you can't see "Report a Problem" next to the item, click the "Report a problem" button. Now click the "Report a Problem" link next to the item.