The Apple push notification servers are upgrading on March 31st. You will need to disable and then re-enable the push notifications on each device in order for push notifications to continue working as normal. For more information on how to re-enable push notifications, please refer to the information provided below.
Step 1: Access your device and tap on the Settings icon ( ).
Step 2: Tap on Push Notifications.
Step 3: Tap on Configuration.
Step 4: Select your device from the configuration menu and disable the push notification toggle switch.
Step 5: Select your device again from the configuration menu and tap on the push notification toggle switch again to re-enable the feature.
Step 6: Tap the Save icon ( ) to save the configuration.