I made several apps and tried to send push notifications to both Android and iPhones. (from both Android and iPhone versions of the apps)
When I sent the iPhone PN, the notification popped up on top of the i-Phone screen with a sound, and also the message got stored in the apps announcement page. (This is how PN are supposed to work.)
When I sent the Android PN, there is NO notification popping up on top of the phone. The message is stored in the apps announcement page. (Problem with this is that the app users will not know about the notifications in a timely manner - until they get into the app and check the announcement pages.)
All of the apps have PN enabled during the app submission process.
So I tried submitting the Android apps to Google Play, the only place to set up PN is on the Service / API page - I have to enter sender id for the Google Cloud Messaging. Now I have the API's and sender ID's for the apps's GCM, but there is no place within the App making platform for me to link the API so that Google can recognize and accept the message when I send it from the app.
I know for IOS, the PN requires a certificate to be stored in the PN page. But for Android, I don't see anykind of certificate or API key to be stored in the PN page.