Facebook like button plugin – error

Hello,

I have a problem with I cannot figure out myself for long time: I instaled

Like-Button-Plugin-For-Wordpress

and go to page, press like button and get an error:

“The page failed to provide a valid title. A page can specify a title using a meta tag of the form <meta property=”og:title” content=”[title]”/>.”

I check the source, and I find such meta tags:

<!-- using Like-Button-Plugin-For-Wordpress [v4.5.2] | by Stefan Natter (http://www.gb-world.net) -->
<meta property="og:site_name" content="test name"/>
<meta property="og:type" content="blog"/>
<meta property="og:title" content="test name"/>
<meta property="og:url" content="http://darius.freeiz.com/wordpress-facebook"/>
<meta property="og:description" content="Just another WordPress site"/>
<!-- using Like-Button-Plugin-For-Wordpress [v4.5.2] | by Stefan Natter (http://www.gb-world.net) -->

At first I there was not the title in the tag, it was empty. But I add title, and nothing changes.

Maybe the facebook caches it I think. But how can I test if it caches? How can then I clear the cache it is the problem?
You can check a live page here:

http://darius.freeiz.com/wordpress-facebook/