Question regarding showing of pictures on Facebook

Hi! :) I have problems with the showing of pictures when I post this page or posts from it on Facebook: https://www.elchocker.se/ If I post https://www.elchocker.se/ on Facebook the big photo on the first page is not showing. I tried to handle it with YOAST plugin, putting in the photo there in the social media and the plugin says that it should be showing, but it does not. I have another Lucida Theme - https://www.forbjudelchockertillbarn.se/ - If I post this on Facebook the big picture on the first page is showing. Why is it like this? Any idea? They are the same theme, Lucida and I can't see any other difference. Please let me know if you have any idea on how to handle this. Thanks! Best, Peter :)