I'm pleasantly surprised I was able to download, install, and register without any issues. Way to go so far, SE. Now, I just pray the version update goes smoothly. This is where you show us whether you have your act together or not. I'm keeping my expectations low considering how poorly their update server has been known to perform in the past.
If it makes the people who haven't gotten their codes yet feel any better, I got mine for the ultimate seekers collection. When I used it under my account, it created a new account with everything registered to it. :/
I think you clicked the wrong option, although to be honest it's not terribly clear. I don't know why they're so obtuse. Why can't they just have a button that says "CLICK HERE TO REGISTER GAME AND EXPANSION CODES" instead of "Add a Service Account." That's not intuitive. It's not even a case of Engrish. It doesn't make sense to anyone but them.