Looks like it’s down to your site being loaded over https, and the Pinterest link is http, your server is refusing the connection. I amended the link code in my developer tools and it worked ok – https://ge.tt/5yleKJd1/v/0
Would you be happy to try and make a small change to the simple-share-buttons-adder.php file for me, to see if my thoughts on a fix would work?
// pinterest share link
$htmlShareButtons = "<a class='ssba_pinterest_share' href='javascript:void((function()%7Bvar%20e=document.createElement('script');e.setAttribute('type','text/javascript');e.setAttribute('charset','UTF-8');e.setAttribute('src','https://assets.pinterest.com/js/pinmarklet.js?r='+Math.random()*99999999);document.body.appendChild(e)%7D)());'>";
To…
// pinterest share link
$htmlShareButtons = "<a class='ssba_pinterest_share' href='javascript:void((function()%7Bvar%20e=document.createElement('script');e.setAttribute('type','text/javascript');e.setAttribute('charset','UTF-8');e.setAttribute('src','//assets.pinterest.com/js/pinmarklet.js?r='+Math.random()*99999999);document.body.appendChild(e)%7D)());'>";
Tiny change, removing the ‘http:’, hopefully this should do the trick for you.
Is there any reason you’ve decided to run the whole site on https? Only reason I ask is at a skim I couldn’t see anywhere that sensitive information is entered?