Hi,
The problem is, that the featured images are not set, and there are no actual image elements on the page either. The plugin tries to get the featured image first, then the “img” and different attributes on “div” elements. The images within the smart slider module are coming from a slider shortcode, which probably is not registered within ajax requests, or the slider is not yet loaded at that time – so those the plugin cannot fetch.
I recommend setting a featured image for each item if possible, as it is great for any plugin/custom code that needs to request an image for the posts.