Hi,
The issue comes from the plugin called "System - Mobile Page Optimizer". It tries to avoid the loading of the images on the pages by adding a srcset attribute to the images of your products in their "img" tag with the content of the image file. However, for some reason, the content of that srcset is a 1x1 pixel image instead of the data of the image. Thus, you think the images are not there because the browser displays that 1x1 pixel image instead of the normal image.
If you deactivate this plugin via the Joomla plugins manager, you'll see the images appear again.
So I would recommend contacting the developer of the plugin to report the issue, and in the meantime, deactivate it via the Joomla plugins manager.