wrong featured image when sharing post on facebook

Short answer, because by default, Facebook just randomly picks a photo. They used to allow you to pick the image, but that option seems to have disappeared.

They do use the Open Graph metatags, and there is a plugin to help with that.

https://www.ads-software.com/plugins/facebook-featured-image-and-open-graph-meta-tags/

I’m not familiar with the Sociable plugin and whether it has the same Open Graph features.

You can post your question in the support forum for that plugin here:

https://www.ads-software.com/support/plugin/sociable

At the rate Facebook changes things, it’s often hard to know if advice works, so be sure to look at recent advice.

Thanx for your help Matt!