Did you include the dashes and have the letters in lower case? I'm not sure if that is required, but I just redeemed both my codes and that's what I did. I also went directly to the Vault and clicked on Redeem Code at the bottom of the page, rather than going to the D:OS and DC websites first, though that shouldn't make a difference.
Email support@larian.com, with the error you are getting (possibly from the address you used for your Larian Vault account), and a scan or photo of the cards clearly showing the codes.
