Due to Facebook’s decision to close the oEmbed end point for embedding Facebook links, the block will not work anymore after October 24, 2020. Publishers who want to embed Facebook links into their sites will require a developer account and an appid, and provide an authentication token with their call to the endpoint. Facebook Documentation: create an app
WordPress leadership reached out to Facebook but it seems the policy change is final. Apart from alerting users here and in other places, WordPress contributors can’t do anything about it.
Facebook Embed block allows you to add Facebook posts to your post or pages. Keep in mind that the post needs to be public in order to add it.