Hi Eduardo,
In this case, i suggest you to check out the access permission settings in your .htaccess files or sh404sef plugin’s configuration to make sure that all images in image sources can be accessed by the gallery extension (JE Lightbox module and Sige Plugin). Remember to clear JAT3 cache each time after saving any updates.
The reason that I got the 403 Forbidden errors on loading the images when i checked out your installed gallery extensions. In addition, the images were displaying finely on light box when I tried to use Sige plugin on the JA Elastica demo site.