Thumbnail doesn't appear on Facebook and Google+

Question

No page on my website, for example: http://insin.tk/komunikace-v-pocitacovych-sitich/ doesn't show thumbnail on Facebook or Google+ pages. When I insert link to Facebook or Google+ text area to share new post, preview shows without thumbnail.

My website is built on WP and I tried many plugins to fix this problem but nothing seems to help. For pages that I'm testing I have setup the featured image and I have also images in the page. I hope that all required meta tags I have set correctly.

I really don't know where is problem. I will be pleased for every suggestion.

Answer 1

The image URL that Google picks out returns a 500 error.

https://www.google.com/webmasters/tools/richsnippets?q=http%3A%2F%2Finsin.tk%2Fkomunikace-v-pocitacovych-sitich%2F

http://insin.tk/wp-content/uploads/2014/05/komunikace.png

Answer 2

Use the Structured Data Testing tool to help determine what the Google crawler can see.

Use the Facebook object debugger to help with the Facebook side of things.

Try setting the "featured image" on your WP site. Also, there is a good plugin for OG called Stumbleupon and Digg Thumbnail maker that may be of help.