Shortcode no longer working

Up until recently, I have been using the following type of code on my site landing page without any issues to allow users to circumvent a login:

<p style=”text-align: center;”><strong>[su_button url=”https://medstats.mvm.ed.ac.uk/scope-of-site/” style=”3d” background=”#782def” color=”#FDFEFE ” size=”10″]Logged in already or want to skip logging in? Click here![/su_button]</strong></p> . While the code is allowing redirection to the desired ‘scope of site’ page once a user is logged in, it is no longer possible to use this code to avoid a login.

Have you any suggestions, please, as to what may have led to the change and any updates to code that I may need to make to allow the button to function as previously, thus avoiding a forced login?

The page I need help with: [log in to see the link]