After much time messing with this I just need to share to hopefully save someone time.
So you shared your WordPress posts to Twitter and Facebook and the image associated with the link is empty! Ugh!
Visit https://developers.facebook.com/tools/debug/ and scrape your site when you have added a photo to your featured image or update your homepage icon in wordpress via mobile app.
Visit https://cards-dev.twitter.com/validator to whiltelist your summary card.
Hope this helps! Would’ve saved me lots of time!