Facebook is reportedly dropping support for customizing link previews you don’t own. Going forward, you will have to verify your domains on Facebook Business Manager to be able to customize a link’s title, meta description or image when you sharing the link to Facebook.
Facebook is doing this to prevent misuse of link customization for domains you don’t own. This effect goes live from Dec 18, and this blog post has detailed description on what you should do to verify your domain.
If you are a website owner, publisher or a webmaster in general, you should read that post and act on it as soon as possible.