Facebook App Won't Update
Edit: this seems to be a concern that Facebook know. It's an issue with the Facebook app, as well as not a generalised Play Shop concern.
This is what benefited me at least.
- Settings > Apps > All > Google Play Store, Clear data and Clear cache
- Settings > Apps > All > Google Play Solutions > Manage area, Clear all data and Clear cache
It doesn't harmed if you restart your phone prior to you attempt upgrading facebook once more. And also, the mount was SLOW. Simply a minimum of 4-5 mins. However, it did job. If not attempt to uninstall it, or simply wait on a solution.