Wrong Image When Posting to Facebook from iOS

When I share a post from my blog (https://www.daleisphere.com) on iOS to Facebook, the image that shows up in Facebook is the Twenty-Seven header image instead of the page’s featured image or the first image from the post, as I would expect.

The result being that every time I share a post (on my iPhone) to Facebook, they all have the same thumbnail. I would really like the Featured Image or the first image in the post to be the thumbnail that shows up in the Facebook post.

Any ideas how to make this happen. I believe it used to work that way under my old theme – though I haven’t blogged in awhile and I’m not 100% sure.

…Dale