I use Firebase Cloud Functions for sending notification via Cloud Messaging to iOS device. `sendToDevice` method works great and returns success promise without any error or warning in Firebase Functions logs, but on iOS, notification is not showed. If I send notification from Firebase Notifications dashboard, it works great and notification is showed on the device. I don't know where I can have bug. It's possible that bug is on iOS app side, even when it works like I said?

Firebase configuration:

```
 var functions = require('firebase-functions');
 var admin = require('firebase-admin');
 var config = functions.config();
 admin.initializeApp(functions.config().firebase);

```

Part of cloud function:

```
APP.services.firebase.admin.database().ref('tokens/' + userId).once('value', function(snapshot) {

    var userDevicesTokens = [];

    snapshot.forEach(function(childSnapshot) {
        userDevicesTokens.push(childSnapshot.key)
    });

    if (userDevicesTokens.length === 0) {
        console.warn('No tokens for user');
        return;
    }

    var payload = {
        data: {
            title: options.title,
            text: options.text,
            type: options.type,
        }
    };
    APP.services.firebase.admin.messaging().sendToDevice(userDevicesTokens, payload)
        .then(function(response) {

            console.log("Successfully sent message:", response);

        })
        .catch(function(error) {
            console.log("Error sending message:", error);
        });

})

```

Firebase Cloud Functions log:

```
11: 52: 43.952 AM info newChatMessageTrigger
Successfully sent message: {
    results: [{
        messageId: '0:15016....'
    }],
    canonicalRegistrationTokenCount: 0,
    failureCount: 0,
    successCount: 1,
    multicastId: 589....
}

11: 52: 22.760 AM outlined_flag newChatMessageTrigger
Function execution took 604 ms, finished with status: 'ok'

11: 52: 22.252 AM outlined_flag newChatMessageTrigger
Billing account not configured.External network is not accessible and quotas are severely limited.Configure billing account to remove these restrictions

11: 52: 22.252 AM outlined_flag newChatMessageTrigger
Function execution started

```