Backer code expired


I received an email with a two backer codes to choose from back on 2/18/16. At the time I wasn’t playing much, but it said the codes had no expiration, so I held on to it so I could decide which option to choose. Now that I have the game on android, I play a lot more, so I tried to redeem the code, but despite the email saying it has no expiration I still receive a message that the code has expired. What can I do?