Even if you register for the public program that doesn't guarentee that you get access to the profile on Apples website in order to update to the public beta. It's a "closed" public beta, or "invite only." I've been signed up since the middle of the 8.3 public testing and nothing.
You didn't get in because you signed up in the middle of 8.3 testing. "Invites" we're done the day 8.3 public beta started. (Though even if you did sign up before 8.3 started it still wouldn't have guaranteed a spot.)