I was having a considerable amount of trouble getting this plugin to load correctly while using Safari for some reason. It came up very quickly with Firefox and Chrome with no problems using those two browsers.
Then coming here to read about the problems people were/are having with the plugin being really slow or not loading at all and found that having
wp_footer(); in another place other than directly right above the closing body tag did the trick!
So for those that might have a custom theme and the
wp_footer(); is being called elsewhere other than right directly above the closing
</body> tag, put it right above that and it should now be working fine.
At least in my case. As I mentioned, this only happened when using Safari. Firefox and Chrome still worked fine.