according to their scraped info they have the correct og:title but don't display it, might be because of the arabic(?) characters
here is a debug of this site and it works fine https://developers.facebook.com/tools/debug/og/object/?q=https%3A%2F%2Fcommunity.nodebb.org
edit: you might have to set opengraph locale with
<meta property="og:locale" content="ar_AR" />
you can just add this on your admin page under appearance > custom html & css > custom header
R