To use the article feature image as a notification icon, enable the option “Use the post's featured image for the notification icon.”
However, there are certain conditions,
- Your theme must support the feature image option. If it does not, then you must contact the theme author.
- Another way to check is by looking into theme editor
Appearance-> Theme Editor, the
Find functions.php file & post-thumbnails. It may look something like this
Add_theme_support( ‘post-thumbnails’ );