From: WordPress.org Support: https://wordpress.org/support/article/instagram-embed/
Due to Facebook’s decision to close the oEmbed end point for embedding Instagram 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 authenication 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 other place, WordPress contributors can’t do anything about it.
The Facebook embed block was removed for the Gutenberg plugin version 9.0 and will be removed from the upcoming WordPress core version in 5.6″