To display a link preview of your post Facebook takes the information it needs from the OG (open graph) parameters defined in the meta data of this post on your website.
If you have trouble posting your blog posts with images on Twitter and Facebook, it might be related to missing Open Graph tags in the meta data on your website. You can find more information about Open Graph tags and Twitter card tags here:
What are open graph tags and what do I use them for?
If you have already shared a post on Facebook and have changed the image in the meantime, Facebook might not have recognized the change.
To make sure Facebook reads the correct image parameters, please check the URL of your post with the Facebook Sharing Debugger.
With the Sharing Debugger, you can see the information that is used when your website content is shared on Facebook. This is how you can refresh this information for any URL:
If you now share your blog post with Blog2Social again, the image should appear correctly in your Facebook post.
Tags: Facebook, images