Unable to upgrade my Heavensward license

So I picked up Heavensward regular digital edition before Early Access started, and have been playing since. However I recently purchased the physical collectors edition and cannot find a way to upgrade my account.

I tried going to "Enter Item Code" on the Mogstation, however it keeps telling me that my code is invalid (double checked it!). There are no other obvious buttons to upgrade my license.

Am I missing something obvious here?

http://puu.sh/iM3IE/31c35a69ef.png

You click the big Digital Upgrade button.

That is used for BOTH the upgrading of the base game, and the upgrading of the DLC.

That's what I thought, but that's if you want to digitally upgrade and buy it direct through the Mogstation. I have the physical copy, with the code printed on a slip of paper, from inside the game case.