Pinterest Not Picking Up Feature Image of Post if “Hidden”

I wonder if there is something non-standard going on with the Pinterest social media share button, as it only works when the Feature Image is “Unhidden” in the theme settings, and the SEO plugin author has assured me that the meta tag “og:image” is present (no matter the theme Feature Image setting) and it should work no matter if the image is shown or not. Facebook and Twitter shares load the image fine.

I was hoping you could look into that to see if the Newsup’s Pinterest sharing function is working in the standard way?

P.S. Sharing buttons for Mix and Reddit would be nice. :>