Why is the notification handler not invoked when launching my app from the iOS Springboard?

Due to an Apple design decision, when manually launching your app from the iOS Springboard, any notifications received in the background aren't made available to your application, even if they haven't been dismissed by the user.

As per the Local and Remote Notification Programming Guide:

• If the app icon is tapped on a device running iOS, the system furnishes no information about the notification.

To work around this restriction, the recommended approach is to fetch all updates and pending notifications from your backend when your iOS app is launched.