Pushing Notification in alpha

Hi All,

I am trying to push a notification by enabling dev environment.
I followed the below tutorial:

But I am getting the following error:
error queueing push notification null

I have followed exact steps as in video.
Below is the system information:

Cordova CLI: 6.2.0
Gulp version: CLI version 3.9.0
Gulp local:
Ionic Framework Version: 1.2.4
Ionic CLI Version: 1.7.15
Ionic App Lib Version: 0.7.2
Node Version: v4.4.1

Any help would be appreciated.