When you share a post on Facebook, or when Jetpack Publicize publishes a post to your Facebook page, Facebook crawls the page and looks for Open Graph meta tags in the head to build a complete post preview (with an image, title, description, …).
Jetpack automatically creates these Open Graph Meta tags for you unless you already use another Open Graph plugin, in which case we let the other plugin handle things. Looking at your site, you seem to be using the Yoast SEO plugin to handle Open Graph Meta Tags.
The tags appear to be correct right now, Yoast SEO seems to do its job properly, but for some reason the image wasn’t available to Facebook when it first accessed your post to get some information and build a post preview. This often happens when a lot of actions are happening on your site when you hit the Publish button; your site gets slower just when you publish, and Facebook can’t reach your site to get info about the post.
If this keeps happening, I’d recommend that you review your list of active plugins and make sure you do not use any plugins that may be slowing your site down when hitting the Publish button.
I hope this helps!
