Welcome to Android Central! To reset all app preferences, go to your App Manager and tap the menu button--I think the option should be there for Samsung devices. On most non-Samsung devices, you got to Settings>Apps, tap Menu, and then tap Reset App Preferences.
Keep in mind, though, that there might still be some issues with Facebook videos. I've seen some threads about problems playing video from Facebook, but I'm not sure what the root cause of it is.