Why can't I buy music for my iPhone?

I have the album Long Live A$AP on my iPod, I got an iPhone 5 and when I tried to REdownload it from iTunes it says purchased. I'm using the same apple ID account and I would like to know how I can get it on my iPhone.

I don;t understand why you'd need to REdownload it. If you already bought it it should already be on your computer. If not, why haven;t you downloaded it using "Transfer Purchases"?