Clicking on related post doesn't work

Hi,

I’ve installed the plugin and really like the functionality… except that whenever I try to click on a related post, the screen greys out and it tries to appear in a lightbox of some kind but then fails with error.

Any ideas what’s going on?
e.g. try the sample related posts at the bottom of this post: http://tactustherapy.com/speech-therapy-apps-for-kids/

Thanks,

https://wordpress.org/plugins/easy-related-posts/