Please Help Me Test My Membership Plugin

Hi Peeps

Please help me test out my membership sign-up process and give me feedback on the flow:

http://harounkola.com

With a link to sign up for a free membership:
http://harounkola.com/join/?action=registeruser&subscription=19

But its not working as I think it should.

First, as a test user, I sign up for a free membership, after I add in all my info on the register page, and click sign up, I'm redirected back to that same page:

Then when I log in as an admin, and I look at the membership info, this test user is listed as inactive, as per the screenshot.

What am I doing wrong?

Thanks
Haroun