FCM topic - Cannot subscribe to topic: xxx with token: (null) - iOS

I'm getting this error from Firebase Messaging API:

[Firebase/Messaging][I-FCM002010] Cannot subscribe to topic: /topics/testTopic with token: (null)

But before:

Messaging.messaging().subscribe(toTopic: "/topics/testTopic")

I'm printing out the token like this:

print("TOKEN: \(InstanceID.instanceID().token() ?? "NO TOKEN")")

The result is:

TOKEN:cXPhGQ_inE4:APA91bEKZF5depHmIm9gDliCFRCRcnJf5LYy5FMg6nhpWvKU3o3HEtr1WTBHUiCZXT4XzhVg2oqXzhtfrgf83brtLdqXii546644ciMPO80tri4JPueQBClKbaomEfoh54ku8E2lw


So the token isn't *null*.

Am I doing something wrong? Anyone some help?

I had similar problem. The solution was to invoke `FirebaseApp.configure()` first:

FirebaseApp.configure()
Messaging.messaging().delegate = self

instead of:

Messaging.messaging().delegate = self // this brakes FCM
FirebaseApp.configure()

The most ideal place to resolve this issue is in the MessagingDelegate method didRefreshRegistrationToken.

func messaging(_ messaging: Messaging, didRefreshRegistrationToken fcmToken: String) {
// TODO: subscribe to topics here
}

The problem was that I wanted to subscribe in `didFinishLaunchingWithOptions` but in that point not all services were set up.
**The solution was** to subscribe in the delegate `didRegisterUserNotificationSettings`.

In MessagingDelegate try it:


func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
Messaging.messaging().subscribe(toTopic: "/topics/testTopic")
}