Coke Fridge: Dude, where's my song?

I had just inserted the digits from 4 new Coke caps and iTunes had registered 1 free song in my iTunes, but when I wanted to download a (free) song 3 hours later on my Macbook, it said no credits available. When I returned to the main Comp where I had gotten the free song and the credit had appeared in my iTunes app, it said no credits just the same. I am quite sure that nobody else is using my iTunes account. Where's my free song?

Mat

Edit: It does work now, but only on the PC, not on my Macs.