That thread explains it. You were supposed to get an email with the activation code, but for some reason lots of those emails didn’t go out. You need Support to get the code for you (I’m chatting with support for mine right now as I type this).
EDIT: Support just told me that it can take up to a week after delivery to get the emailed code, and told me to wait a week and then contact them if I still don’t have it).