Here’s what I got back from the developer…
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The reason no image is being pulled into the shares on Facebook, G+ or Pinterest is that there are no images specified on your forum page. I recommend explicitly setting an image in the Facebook Open Graph image (og:image) meta property on your page code.
For context: The ShareThis widget tries to identify images on the page to use on the social sharing services. It looks to see if either the og:image tag is specified in the head code of your page; if there is, it uses that. In your case it’s including the following blank file: https://s0.wp.com/i/blank.jpg *
We confirmed that that’s the file being included by running your URL through Facebook’s Object Debugger, found here: https://developers.facebook.com/tools/debug/og/object/ You’ll see the above file name in the og:image section; when you open that URL, you’ll see it’s a blank image.
If you update the URL to something that includes an image you want, then that is the image that will be pulled when you or a user shares a post via the ShareThis buttons. To do this, you’ll want to add a tag that looks something like this between the head tags of your page code:
<meta property=”og:image” content=”http://sharethis.com/images/logo.jpg” />
To learn more about the Open Graph tags, feel free to check out our Help Center article here: http://support.sharethis.com/customer/portal/articles/475079-share-properties-and-sharing-custom-information#Open_Graph_Tags
Hope that helps! Please don’t hesitate to let us know if you have additional questions about this topic or another.
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* I believe this blank image came from jetpack publicize – I didn’t set this up so if there is an option to add a default image there, I suggest you do that or you’ll get a blank one.
In the meantime, I went into Yoast SEO plugin> social links and selected Twitter with large image. I am testing to see if this solved the problem. I also did add a featured image in Simple Press as recommended by another user here 🙂
Great support and feedback from them.
Good luck –
Meredith