Im using Ultimate SEO plugin but even that did not help to make a facebook post with image.
So i had to manually add the og:image.
Here is what I did and its working for me: /qa-theme/Infinity-Theme/qa-layer-base.php, around line 50 to 60 find: $this->output('<meta name="viewport" content="width=device-width, initial-scale=1.0">');
In the same function just below the line mentioned add: $postid = @$this->content['q_view']['raw']['postid'];
if(isset($postid)){
require_once QA_INCLUDE_DIR.'qa-db-metas.php';
$image = qa_db_postmeta_get($postid, 'et_featured_image');
if( (!(empty($image)))&& (substr(qa_get_state(),0,4)!='edit') )
$this->output('<meta property="og:image" src="'.qa_opt('it_featured_url_abs') .'featured/'. $image.'" />');
}