Redirect after registration not working


I have installed Membership 2 Pro on my site. I have set up a non-payment membership group, inserted the shortcode for registration ( ( and defined the 'Thank-you page' that users are directed to upon registration. However, when users insert their details and press the 'Register' button, they are kept on the same page with the following url being showed

From what i can tell there is a problem with the user sync because when the user registers they get added as a wordpress user but not as a Member. (And yes the ID of the registration form is correct)

Please can you advise on how to fix this asap?