Facebook like button is not working

I am using facebook like button plugin from wordpress site but its not working properly…
I used these 2 tags in header….

<meta property=”og:image” content=”<?php echo wp_get_attachment_thumb_url( get_post_thumbnail_id( $post->ID ) ) ?>” />

<meta property=”og:image” content=”<?php echo(get_post_meta($post->ID, “thumburl”, true)); ?>” />

Pls check here https://www.krazytech.com/technical-papers/artificial-intelligence-on-expert-systems

And someone suggest me wat exactly to do ??

What shd be the target url ???