I've received my 290x and created an account on http://www.amd4u.com/getbattlefield4
I've went to redeem the BF4 voucher and the system states: Error: UID is not valid.
There seems to be a few forum posts on this issue. I've checked to see if I need to submit proof of purchase, however this appears to be for US residents only.
I've raised a support request: Support_ID28938
Is it possible my code is no longer valid? (I hope not)