Hi Aureliavl,
First of all, thank you for the purchase!
Let’s start with the following: please go to the “Image Slider” tab of the Theme Options panel, open any of the slides you’ve uploaded (by pressing the little pencil-and-paper icon on the right) and check if the “Image URL” field content ends with your image file’s name (i.e. “image.jpg” or “image.png”). Then go to the “Header” tab and check if you’ve selected “Image Slider” for the “Content of the custom header” option. Also note that the slider will appear on pages, not on individual posts. In case this does not solve the problem, please provide your website’s URL and admin login/password (sent them to support@satoristudio.net) so that I could troubleshoot the issue in the quickest possible manner.
Sincerely,
Andrew | Satori