Hi,
There is a second jQuery script loaded on the bottom of the page source, which wipes out all previously loaded extensions, causing the error.
This is the problematic line:
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.4.1/jquery.min.js"></script>
That should be removed, as WordPress already loads a jquery instance at the page header for plugins to attach to. It will resolve the issue as well.