samsung note 2 androind version 4.1.2 cannot connect to wifi and authentification error occured

I'm using samsung note 2 GT-N7100 android 4.1.2, the phone connection to wifi cannot be used since 12/11/2017. Even though the correct password had been keyed in , it is still show authentification error occurred. Pls assist on urgent basis as i'm fully count on wifi support

Welcome to Android Central! Have you already tried forgetting the network and reconnecting? Also, try rebooting the router by unplugging its power for 10 seconds.