First, please check the following details.
1) Turn the notification for Hakuna off and on again from your device settings
2) Check if all notifications for Hakuna from your device settings are turned on
If the problem still persists, go to the 'My Page' and select 'Help center'. Then submit a request with the following information.
1) Device name (eg. iPhone 6)
2) iOS version(eg. 8.3)