Social Buttons not displaying image

Hi,

I’m having big problems, trying to make ANY(!) social plug-in work with WooCommerce under the Enfold theme. I’ve tried to trouble-shoot all day today, but no result :(

The social buttons appear next to the product, ok. But when I click them – for example to share or like a product on Facebook – the product image/thumb does not appear on the Facebook post.

First I thought it may have to do with some of my theme customisation. So I re-uploaded the original Enfold theme, without any custom.css whatsoever. And also did a clean install of the WooCommerce plugin. My products have a standard “Featured Image”. But this image just doesn’t want to display on Facebook.
Tried different browsers, disabling ALL browser-plugins. No luck.

Even if I manually copy & paste the product URL into Facebook: Facebook only shows the URL text, but not the image.

I’ve tried three different “social button” plugins. None of them work:
Jetpack
WooCommerce Facebook Like Share Button
Social Sharing Toolkit

I used to run a few plug-ins (like “W3 Total Cache” and a few others). Deactivated them. Still: it doesn’t work. Whatever I try – the Product Images just WON’T display on Facebook or Google+ …. or any other social media.

Can you please help?