Why does ionic app can't register with GCM after packaging it into an apk file?

The Ionic app with WordPress REST API using a WordPress push plugin when packaged through Ionic Package Service displays API data and functions correctly except registering with Google Messaging Service. The app registers to GCM the all android phones and I can receive notification if I install it on any Android phone from the project source files. But, when I use ionic package service and use the apk file to install the app on any phone then it can’t register itself to GCM. Does Ionic Package service drop cordova.js or and I missing something else? For development tests do I still have to follow all the steps like a release build based on Ionic documentation?