The notification feature for the SchoolFox app may not be enabled on your phone. Click on your mobile phone settings (not in the app) and on "Notifications". Here's an overview of all your apps and you can choose for which apps you want to receive notification from SchoolFox in the future.
On some smartphones, the battery settings also block incoming notifications. Please select Settings>Battery in the menu and make sure that the SchoolFox App is not closed for energy saving reasons.