Q:

Add another profile link not working

None of the "add another profile" links on the Event/Online Registration tab are working.  The page just refreshes.  This is the first time I have tried to edit an Event with this version of civicrm -- I recall this this worked previously.  As shown below, my form lacks quite a few buttons. 
Example from demo site:

Example of my form:

A:

Thanks to Kevin in the comments section.  It was a plugin called Kadence Slider causing the problem.  This plugin and the Kadence themes are not compatible with CiviCRM.