Good question. I had this issue just now and it seems like many others will as well. Here's what happened to me:

I signed up for the wait list a few days ago, and today when new accounts became available I attempted again to sign up (using the same email address). At first I received a message that couldn't open an account because I was already waitlisted.

BUT because I'm so persistant, I clicked around, and the site will let you authenticate thru Facebook or Reddit (for Reddit, you need to have a certain amount of Reddit points/cred/whatever their rewards system is called).

After you're authenticated, the site will disregard the waitlist and allow you to create your account.

I hope this helps anyone else experiencing similar difficulties!