Receiving Push Notifications while in background

application:didReceiveRemoteNotification: will call in the background only when you have added content-available key with value 1 into the notification payload. In case of the Urban Airship, you can send Test Push under the Setting tab. Sample Payload for Push Notifications:

{
  "aps": {
    "alert": "aaaa",
    "badge": "+1",
    "content-available": "1"
  },
  "device_tokens": [
    "86BA71E361B849E8312A7B943BA6B26A74AB436381CF3FEE3CD9EB436A12A292"
  ]
}

Apple has clearly mentioned in his documentation....

For a push notification to trigger a download operation, the notification’s payload must include the content-available key with its value set to 1. When that key is present, the system wakes the app in the background (or launches it into the background) and calls the app delegate’s application:didReceiveRemoteNotification:fetchCompletionHandler: method. Your implementation of that method should download the relevant content and integrate it into your app. https://developer.apple.com/library/content/documentation/iPhone/Conceptual/iPhoneOSProgrammingGuide/BackgroundExecution/BackgroundExecution.html

From the APNS programming guide :

Let’s review the possible scenarios when the operating delivers a local notification or a remote notification for an application.

The notification is delivered when the application isn’t running in the foreground. In this case, the system presents the notification, displaying an alert, badging an icon, perhaps playing a sound.

As a result of the presented notification, the user taps the action button of the alert or taps (or clicks) the application icon. If the action button is tapped (on a device running iOS), the system launches the application and the application calls its delegate’s application:didFinishLaunchingWithOptions: method (if implemented); it passes in the notification payload (for remote notifications) or the local-notification object (for local notifications).

If the application icon is tapped on a device running iOS, the application calls the same method, but furnishes no information about the notification.

I believe the last sentence describes your case, and explains why your application gets no information about the notification.

didReceiveRemoteNotification is calling ONLY if app in foreground or if app is just launched or is bought from background to foreground

link in Apple and some question