In case you haven't heard about, or encountered the issue firsthand, there is currently a problem with redeeming WoW TCG Loot Codes in-game.
The Blizzard techs are currently looking into the problem, but the issue has yet to be resolved.
Here are the official blue posts concerning the matter:
Good morning folks,
While I dislike making a post with little information, I did want to let everyone know that this has been forwarded to be looked into.
I really have no further information at this time, but we'll try to keep you updated.
If you have experienced this, you may wish to bookmark this post and check back periodically.
Thank you very much for your patience.
Then just recently we received this update…
Not much of an update, but I did want everyone to know we've not forgotten about this,it's still under investigation by our techs.
To keep abreast of the situation, you can follow the official thread here.