If you are unable to move on to the next screen, it is usually because you have not completed and saved information on an earlier screen.
Make sure you complete all sections, this may include ticking boxes and selecting no for sections that are not relevant to you.
You can view this video on our website that goes through how to complete online registration. 
New students, makes sure you are logging in with your University username and not your application details. IF you have been logged in with your applicant details we would also recommend clearing your cache or trying a different browser.