Featured Image Publicize

When you share a post on Facebook, or when Jetpack Publicize publishes a post to your Facebook page, Facebook crawls the page and looks for Open Graph meta tags in the head to build a complete post preview (with an image, title, description, …).

Jetpack automatically creates these Open Graph Meta tags for you, and looking at your site, the tags appear to be working properly, and include your posts’ Featured Images.

You can see what Facebook sees by entering one of your posts’ URLs in Facebook Debugger:
https://developers.facebook.com/tools/debug/og/object?q=http%3A%2F%2Fterre-humanisme.org%2Fth-participe-au-salon-artemisia
https://i.wpne.ws/XvCw

Unfortunately, it seems Facebook chose to ignore these tags, and picked a different image instead. I’m afraid there isn’t much you and I can do about it. If it keeps happening, I’d recommend contacting Facebook to let them know about the issue. You can do so here:
https://developers.facebook.com/bugs/trending/

Ok thanks.