iTunes pre-order not downloading.

Hi all,

I've had this issue come up a couple of times recently where I will have pre-ordered an album and, while the first few singles will download, when the album gets released the rest of the songs will not. I am running iTunes on my PC, and have tried singing in and out of my account, looked in my store for available downloads and there is nothing there, and looking up the album in the store it says that is has been purchased (although only the downloaded songs say 'play' next to them, the others just say 'purchased'). If anyone has any ideas on how to force the songs into my library I would very much appreciate it. Thank you!