Facebook App Not Working after Update
Edit: this seems to be a concern that Facebook are aware of. It's a problem with the Facebook app, and not a generalised Play Store issue.
This is what worked for me at the very least.
- Settings > Apps > All > Google Play Shop, Clear information and also Clear cache
- Settings > Apps > All > Google Play Services > Manage area, Clear all data and Clear cache
It does not injured if you restart your phone prior to you attempt updating facebook once more. And also, the install was SLOW. Simply a minimum of 4-5 mins. But, it did work. If not try to uninstall it, or simply wait on a solution.