REST API call is not working when app is in background

I am using iPhone 6s(12.5.7) and had set up for receiving silent notifications on the device.

I am trying to call REST API under didReceiveRemoteNotification but when app enters in to background api request is not happening. can some one suggest me if i am missing with anything and any changes to be added?

func application(_ application: UIApplication, didReceiveRemoteNotification userInfo: [AnyHashable : Any], fetchCompletionHandler completionHandler: @escaping (UIBackgroundFetchResult) -> Void) {

    ENPush.sharedInstance.sendDeliveryStatus(notificationId:userInfo["en_nid"]as! String,status: ENDeliveryStatus.seen){ response, statusCode, error in
            guard error.isEmpty else {
                return
            }
            print(response ?? "")
    }
})

    print(userInfo.debugDescription)
    completionHandler(.noData)
}