Why Won't My Facebook App Update
Edit: this seems to be an issue that Facebook are aware of. It's a concern with the Facebook app, as well as not a generalised Play Store problem.
This is what helped me a minimum of.
- Settings > Apps > All > Google Play Store, Clear information and Clear cache
- Settings > Apps > All > Google Play Services > Manage room, Clear all information and also Clear cache
It doesn't harmed if you reactivate your phone prior to you try updating facebook again. And also, the mount was SLOW. Just at the very least 4-5 mins. But, it did work. If not attempt to uninstall it, or simply await a solution.