Images on Product Pages (Woocommerce) are opening as a new page

https://www.tristarcctv.com/product/vivotek-vs8401-video-server/ Images are no longer popping up in a lightbox type of setting, they are opening themselves as a new window - having to go back to the product page. I've read through these forums but cannot figure out how to fix this issue. Help will be appreciated. Thank you