Is the album listed in the store e.g. it's not that the availability email has been sent out too soon ? If it is in the store then does the Store > Check For Available Downloads menu option on your computer's iTunes find it, and/or does it show on the purchase history on your account ?
If it is in the store but you can't download it via the Check For Available Downloads option or the Purchased link under Quicklinks in the store on your computer's iTunes, or the Purchased tab in the iTunes store app on your device, then try the 'report a problem' page to contact iTunes Support : http://reportaproblem.apple.com
If the 'report a problem' link doesn't work then you can try contacting iTunes support via this page : http://www.apple.com/support/itunes/contact/- click on Contact iTunes Store Support on the right-hand side of the page, then Purchases, Billing & Redemption