According to a new post on the TERA NA site, the online vendor responsible for player purchases of the game experienced a system failure that has resulted in game purchases not "committing" the buy to En Masse (and has plagued other customers besides En Masse). As a result, players recently purchasing TERA are having access issues. Luckily, the En Masse team is on the ball and has come up with a temporary solution until the vendor issues are resolved.
So here's what we're going to do: we're monitoring our purchase logs to detect when players purchase TERA, and we'll batch these up every two hours and email those players a game code to play TERA. It will be a "trial code" that enables you to get in and play this weekend. When the online store problems are sorted out, you will be automatically upgraded to the full account you purchased (standard edition or collector's edition), never fear.
Read the full post on the TERA NA site.