I'm not sure if I completely understand your problem. Was that a system update or just an app? Are you talking about Facebook or something else? Try going to your settings - apps and clear cache for that app. If it doesn't work maybe you'll need to clear data as well and then sign in again.
This happens to me now after last update on facebook app. Android system, Bought an unlocked phone and it appears to be a system app. Cleared cache which worked for a little bit but its started happening again. Did all the steps above too.
There are some reports of people having problems recently with the FB app. It seems it could be on their side and not your phone. Have you tried clearing data for FB and logging in again?