Why on FB & TW share do not show main image

The plugin shares your home page, please see https://screencast-o-matic.com/i/c3XvQHVU7mx. Could you please elaborate on the issue?

I would like to share a blog post and to show the main image of this post.
In this case it has done well, but other times it did not put the image of the entry. Today he is doing well.
Thank you anyway

https://postimg.cc/RJtMw73X

You can define exactly what gets shared in this plugin https://www.ultimatelysocial.com/usm-premium. Also see https://www.ultimatelysocial.com/making-the-right-image-show-up-when-sharing-on-social-media/