Blank Featured Slider #

In the Featured Slider # I've tried all 4 options: Featured Post Slider, Featured Page Slider, Featured Category Slider and Featured Image Slider. Without any success! Sometimes, It only shows the first image, the others (3) are blank? But right click on blank space to show image in new tab works? Other times they are all blank, even if I refresh the page, and even if I reset it to the demo mode? Plus, in Appearance => Customize => Featured Slider Options => Featured Slider Type I can't even see my original images, unable to bring any modifications... What am I doing wrong? Veetam