This is just a suggestion of what could be the issue. I have a google mail account, so I received the e-mail sent by Snail Games in my Advertisement (or something like that) folder. Just make sure you check all categories thoroughly. I realised the link wasn't in the email, so I refreshed it a couple of times and began to freak out xD but I soon noticed ANOTHER email from the iTunes Store named something like "Snail Games, Inc. invited you to test Age of Wushu Dynasty", the link is in that very email
Hope this helps some of you lot!