I have a WordPress site that was working perfect before moving to a new server, The problem is when I upload any image it uses the original size in all places in my website ( means no re-size for the image - Thumbnail, Medium, and Large), I use FTP to access the Upload folder and I found the original image only without (Thumbnail, Medium, and Large size).
I checked my Media Setting and its okay without any problem, I hope someone could help.