Not only am i having the exact same issue as you, but i also have no order history on the store, since i had to create a new account because they "updated" it. So, not only can i not access the game because its telling me my code is already registered, and i dont have any other code in my email, but i also cant access my order history since the store no longer has any information for me since it forced me to create a new account.

Oh and SE has shit customer service, so i cant get in touch with anyone to see where that other code should be. Awesome.