WordPress 3.5.1 Gallery problem, Images dont Enlarge

Hi

I am setting up a gallery, when I click on images it open on new page and shows the thumbnail of that picture only, when I click on image again it will be enlarged.

The way it should be is to click on any image and it becomes enlarged then I can click on arrow to go to previous or next picture, but now after I click on any image its showing only that image in another page.

Please help me to fix this issue.

This is the url:
https://demo.247pros.ca/image-gallery/

Thanks