Gigabox gallery not working

Hi!
I purchased a plugin but it’s not working at all… I think it depends on my WP configuration… or permission… The plugin is Gigabox Gallery, a really simple photogallery. You can see how it works here:

https://codecanyon.net/item/gigabox-responsive-wp-galleryimage-effect/4453023

I followed all the instructions and put an image into my post…. but nothing happens… The real problem is there’s no assistance, the author has disappeared and doesn’t reply to me! That’s my page:

As you can see, there’s just a simple image, and on click the image doesn’t open a separate page:

https://www.popthequestion.it/galleria/

Please if you have a brilliant idea reply to this post!

Thanks,
Stefano