The image opens fine in a browser, http://3s-pos.com/wp-content/uploads/2016/07/yalla3-300x75.png
This image, http://3s-pos.com/wp-content/uploads/2016/07/verifone136x80.png shows a server error 500. Many, many things can cause that. Using the file manager provided by your host can you see that image in the uploads directory?