Ionic.io push not recieved when app is not running

Hi there,
I am using Ionic Cloud for push notifications in my app.
The problem is the push messages are not received when the app is not in the foreground.
It works well when the app is in the foreground so, the configuration seems fine.

On looking at the"phonegap-plugin-push" project, it says that the latest version( that my app is using ) supports cordova-android >= 6 . Does that mean it won’t work on android < 6 ?(I am using android 5.0.1 for testing.)

cordova-android != Android.
Check here for the supported Android API levels of cordova-android: Android Platform Guide - Apache Cordova