It seems like there is quite a few errors with the site itself. I checked it in Firefox, Internet Explorer, and Chrome and it worked in all but Internet Explorer (not really a surprise) but in IE it shows only 2 errors:
SCRIPT5: Access is denied.
File: xanJX-VvKmY, Line: 1, Column: 1
SCRIPT5: Access is denied.
File: likebox.php, Line: 1, Column: 1
I also noticed that it seems like you have a lot of plug-ins that are not being used or that they might be out of date. I would recommend to disable any that you are not using to see if this changes anything. You might have a conflict between plug-ins (usually not the case if the plug-in is well written).
I would try to clean up some of the things that you don’t need first which is better for security on your site (Disable and uninstall) because the most popular way to hack a WordPress site is through the plug-ins.
Also make sure that all the plug-ins are kept up to date and supported.
Also try updating the WordPress to 4.1 as there is a few security updates.
The plug-in seems to work perfectly fine for me in Chrome and Firefox. Other than that I would wait to see if the developers have some kind of answer.