There are two reasons that an upload will commonly fail.
First, your photo may be too large. Below 500kb works best. Here are directions to resize for several different programs.
Second, the file name should not contain any special characters. For example, joesmom.jpg will work, but joe'smom.jpg will not - the apostrophe causes it to fail. If you have a special character in your file name, do a File, Save As, in your graphics software and save it with a new name. Then, choose that file to upload.