First thing to check is that the size of the image is not more than 2 MB (2048 KB). Thare are also width and height restrictions as maximum width and height is 6000 px. A common reason not to be able to upload your is that the image's name contains characters like ". , ? / % $ !". The image's name should contain only alphabet characters and numbers. And finally the type of the image should be jpg, jpeg, gif or png. Any other image type gets rejected.