To those (like me) for whom the other answer did not work:
In the <head> and </head>section, add
<meta property="og:url" content="https://www.mathnuggets.com/" />
<meta property="og:image" content="https://www.mathnuggets.com/images/fb-logo.jpg" />
<meta property="og:title" content="Math website for your gifted student" />
<meta property="og:description" content="Challenging word problems for gifted elementary students" />`
Then go to FB Linter and enter your URL there to refresh FB's cache of your page.
^^^ Refreshing the cache is important.
与恶龙缠斗过久,自身亦成为恶龙；凝视深渊过久,深渊将回以凝视…
