How to debug push being sent but not received by app?

This [official codelab][1] says:
>
- Run the updated application.
- Hit the device's home button (or otherwise send the app to the background).
- In Firebase console select Cloud Messaging from the Grow section of the left navigation bar. Select Send Your First Message. Set Message Text to "Friendly Chat?". Select the app we connected earlier as the App target. Click Send Message.
- Confirm that the message is received and notification is displayed on the device. The user should receive a notification that takes them back to the application when tapped.

**But I am not seeing the push, nor am I seeing the [debug logs][2]. I have put the google services json in the `app` directory and I'm even using the [reference app][3] (as opposed to the starter app). Further my console shows that the message was completed AND sent.**

Any ideas?

[1]: https://codelabs.developers.google.com/codelabs/firebase-android/#9
[2]: https://github.com/firebase/friendlychat-android/blob/master/android/app/src/main/java/com/google/firebase/codelab/friendlychat/MyFirebaseMessagingService.java#L29-L31
[3]: https://github.com/firebase/friendlychat-android/tree/master/android