From October 24th an API update will break embedded content on WordPress from Facebook and Instagram. This update is removing support for unauthenticated embeds.
This update will work retroactively. This means if you have embedded content from Facebook or Instagram it’s likely to break. Facebook is only offering one solution to meet the new requirements. This involves creating a Facebook Developer account, registering an app, adding the oEmbeded Product to the app, an access token and the app being in live mode.
This isn’t a solution for everyone. However, there are more realistic solutions in the form of WordPress Plugins. You should be able to use oEmbedPlus or Smash Balloon Plugins to bring back support for your embedded content.