My Register Form will not submit

Hi guys, I'm having trouble with my Registration process. Currently I have my site set up so that when the user lands on the front page they click a "Join Now" button which brings them to the subscriptions page which displays a list of my available subscriptions.

They then click to "Sign up" for the relevant subscription and they are then redirected to a Registration page which shows a form to input various user details.

The issue I am having is that when I input the details for a new account and click submit the form just resubmits to the same page....The user is not registered or brought to the Welcome page.

This is the action of the Registration Form:

action="http://incomebrokers.tld/join/?action=validatepage1&subscription=3"

Is there something I am doing wrong? Any advice is much appreciated.

Also I should point out if I change the method from Original Register form to Pop up register form users can register without any issue....however that is not really a fix as I'd ideally like to redirect them to the Registration Form Page as opposed to the Pop up form.