Thumbnails not working after upgrade

Hello!

I just recently installed this theme and since I upgraded to the latest version of WP recently the thumbnails on my homepage gallery is not working anymore. It’s suppose to open up a box with the full size of the image but now its just stuck trying to load it.

I’ve checked everything I could think about to no avail. I was wondering if you might have any ideas as to what is causing this issue all of a sudden. Thanks very much in advance for your time and help. This is my site.