Sign-up Form not showing up

I've set up 2 levels of membership. set up the registration page, enabled the plugin and went to a different browser to test it. I can see the registration page, and on that page it shows the two levels of membership, each with a sign-up button. However, whenever I press a sign-up button it directs me directly to the home page. No registration form. The URL reads /?action=registeruser&subscription=6.

Can anyone show me what I'm missing??

Many thanks!