Hello,
SimpLe Viewer – This type of gallery does not have a lightbox and for this reason the gallery will not be displayed above the entire content of the page (overlay mode). Deep links will allow you to share a page with a specific image (active) in the gallery. In the case of the SimpLe Viewer, your page should have one gallery per page – for everything to work in a friendly and meaningful way.
Demo:
Medium Pet Collection Bed
But as I see you are using SimpLe Slider which will allow you to accomplish your task if you activate Deep Links. In this case, after loading the page, a lightbox will automatically open (overlay mode) and the visitor will immediately see the selected image. And also having multiple galleries on a page won’t cause confusion.
Demo SimpLy Slider:
Dog
Chicken meatballs with tomato sauce
It is forbidden by the rules of this forum to discuss the premium version of the plugin, so I recommend that you use the contact form for premium users in the future.