Open Graph error

I’m experiencing an open graph error confirmed by FB debugger, which says “og:type” is missing (hoewever it is switched ON in the plugin). This mistake results in NO preview image and NO preview text when sharing an article on FB, only a grey frame with the blog URL is shown. What could the reason for this be?

https://www.ads-software.com/plugins/wonderm00ns-simple-facebook-open-graph-tags/