Just to add my own experience, I purchased a $25 gift card from Target yesterday morning. The clerk at the electronics counter had no idea they were on sale but it did ring up for just $15. The receipt indicated that activation was successful. Still, I decided to wait a few hours before trying to redeem. When I finally made the attempt late yesterday afternoon, I received an invalid code response. I called Sony customer support and they could not find the code number in their database. They gave me a support reference number and asked me to email a picture of the receipt and the card to the email address of
support@ebookstore.sony.com. While I never received any additional contact from Sony, I tried to redeem the code again this morning and it worked fine.