I see “User Registration is not allowed” message instead of form, because by default WP not allows User Registrations and PR honor WP setting, so please follow these steps to fix it:
1. login to the WordPress Dashboard
2. Go to General under Settings on Left sidebar menu
3. Scroll the page to where it reads “Membership: Anyone can register”
4. “Check” this box and Hit Save Changes
The above change will let the Registration Form be displayed instead of Warning Message. Please note: PR won’t let you stay on the Login, Registration pages if you are logged in on the browser, so its advice to use 2 separate browsers.
Hope it helps you.