I had the same problem, but I have multiple bungie accounts and ordered 2 shirts for 2 separate players. So, what I did when I received the error, is I went back in to my rewards page and clicked email discount code again. I received a different code the second time around and that code worked.
English
-
I tried to send another code but it must be assigned to my account because it sent the same faulty code twice.
-
That sux. Saw others having the same problem. Hope they fix it.