Facebook is frequently randomly locked by Norton applock even though I keep unsecured it. It is getting very annoying.
Try going into the Android Settings and deleting the App Data for App Lock. Restart the phone and try again. You will probably have to reset all locks in the app when you restart.
I’ve done that multiple times now. I waited until the next update to follow up. Now with the recent update, Facebook along with Facebook messenger are locked every time my phone sleeps, no matter how many times I specifically unlock them or clear the app cache and restart my device. I’ve even cleared my facebook app cache to absolutely no avail. It truly is very frustrating.
Try going to Android Settings - Apps and look for Norton App Lock. Scroll down and clear the app cache. Restart your device and see if this helps.