I downloaded a few of my songs off the album. How do I get them on my library?? It is really making me mad.

I preordered the album Midnight Memories and it told me that as it came out it would immediately be paid for and put on my library. Well it has not done that. iTunes help told me that I just need to go onto "store" and click on "check available downloads" and I did but it only downloaded some of the songs. I tried again and again and it still won't let me download the rest of the album. If you could help me that would be great and I would soo appreciate it.