I seem to be unable to add my Mount and Blade key to my TaleWorlds account. It says it's "Invalid serial code syntax". I purchased the game from Steam, so I'm not sure if that had something to do with it. The key looks like this (X = letter; # = number):
XXXX-#X##-####-####-X##X-##X#
Thanks.
XXXX-#X##-####-####-X##X-##X#
Thanks.