Why Facebook no notification issue occurs?
If Facebook no notification is the only issue which is irritating you then check your mobile's setting. There are high chances that you've disabled the app notifications from the setting of your mobile device. In case of iOS mobile, enable 'Allow Notifications' for Facebook in settings of your phone. For Android mobile, visit the 'Application Manager' nestled in the Settings and tap on 'Notification' on Facebook and switch the same on from Facebook App.