Fixing of images in website for google matched content unit

I have this website enter link description here that contain more than 500 posts. Now I am using google Matched Content Unit. Instead of displaying featured image on "Google Matched Content" ad unit, it is displaying other images in my website. I know this problem is due to missing og:image tag for feature image. I am using All In One SEO plugin for Open graph. It is working somehow but only for new posts and not for the existing posts. My requirement is that "Google Matched Content" ad unit should display images from features images. You can view my website on your mobile devices to see this behavior.