I can't download Perfect Patio Stuff

I bought the Perfect Patio Stuff pack, but then when it started to download, it immediately said there was an error (I think it might been a "directory error", but I'm not sure) and would pause. I tried to "resume" the download several times with the same results. So, thinking I would try again later, I exited out of the little download progress window... but now I can't find a way to bring it back to try to restart the download again.

I checked my Order History in my Account & Privacy tab, and it says the order was successfully completed and delivered... But when I go into the game, even though it says I own the pack, it won't let me do anything with it, and there's still no way to download it.

What can I do to download it?