Changing Featured Picture

If you are using WP 4.5+, there is a problem many of us have noticed trying to upload images, a fix should be out soon. In the meantime, there is an extensive thread here with several workarounds: https://ww.wp.xz.cn/support/topic/http-error-when-uploading-images-17/

The easiest workaround, if you don’t feel comfortable editing your functions.php file or .htaccess file, is to install this plugin which changes the default image editor:
default-to-gd