When I click on the enlarge icon on my site, it doesn’t work for some images in the gallery…sometimes it’s the first one or sometimes it’s some of the later ones. Please check the link in the private content section. You can also try with some other products.
Please deactivate all the third party plugins, clear the cache and check back.
If the problem continues then leave the plugins deactivated and provide with the admin panel login details of the website then we will troubleshoot with default plugins.