Here’s how to fix Facebook not working.
Facebook is one of those services that is hard to live without. You probably use the app to connect with friends, family, coworkers, and the occasional friend, so it’s hard to bounce back when you find that Facebook is no longer working properly. If so, there is an immediate solution available on the Facebook mobile site. This is a lightweight, mobile browser optimized app that can give you almost everything that the Facebook app can give you, including notifications.

Facebook not working? Make it work
First, make sure the app is fully up-to-date on the Google Play store. Facebook frequently publishes updates to its app for security updates and bug fixes. First, open the Android settings and check your available storage. If your device has less than 100MB of available storage, you may need to free up some space to allow the app to update. If that doesn’t help, log out of the Facebook app and then try the download one more time. If that fails, you can try uninstalling the Facebook app, restarting your device, and reinstalling the app from the Play Store.
https://www.not-working.co/facebook