unable to receive notification on my android device

Hi All, I need your help please

I'm using PhoneGap Build (cli 6.4) + phonegap-plugin-push 1.9.2.

1. My app compile and install correctly on my device
2. it registers to Firebase and get a RegisterID correctly
3. From Firebase console I can send a notification message to my device using my RegisterID
4. From Firebase console "message sent correctly"
5. ...but... on my device I don't get any notification in foreground and background mode

What can I do?

Best Regards, Giorgio

PS. this is my notification javascript:

push.on('notification', function(data) {  

     localStorage.setItem('msg', data.message); 

     navigator.notification.alert(

            data.message,         // message

            null,                 // callback

            data.title,           // title

            'Ok'                  // buttonName

        );