On October 24th, 2020, Facebook will institute a change which removes the ability to easily embed “link previews” on WordPress and many other sites using the popular oEmbed protocol.
oEmbed is what allows you to enter a link in your blog or site and present a preview of the target page.
Possible solutions include plugins such as https://wordpress.org/plugins/oembed-plus/, https://wordpress.org/plugins/instagram-feed/
and https://wordpress.org/plugins/custom-facebook-feed/