Add-on Social bar not displaying in some browsers

I have the social share bar enabled for my blog posts but it appears erratic whether it displays or not. On my Macbook it works fine when viewing with Safari but isn’t displaying at all when viewing with Chrome. On my Windows PC it displays fine in Chrome but doesn’t display in Internet Explorer or Firefox !

What could be stopping the social bar displaying in some browsers ?

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