iTunes Purchases Not Downloading

Dear all,

This has completely stumped me: I downloaded a song on my macbook yesterday, and now it shows up in the purchased list on my iPhone, but didn't download. Eventually it looks like it has downloaded but when I 'play' it there is no sound and the counter doesn't go above 0:00. Any ideas?

P.S. I am in the correct account and have re-started the phone.

Any ideas?

All it does now is if I tap the download from the cloud icon in the music app, the spinning circle flashes on and off forever...

David