Getting GCM SenderId failed

Hi, i'm having a problem with GCM. I read the doc about ACS and GCM, and, even if i followed every step, the console shows me this error:

W/com.appcelerator.aps.CCPushService: Getting GCM SenderId failed. No response area in returned JSON. Will try again in 5 seconds.

I explane what i've done at least you can tell me what i did wrong. 1) create a project with cloud-enabled 2) create in the google console a new project and i enabled the "google cloud messagging" and i create a new "server key"; 3) open "myApps" in my dashboard and i select "manage ACS" 4) copy the project number and the server key in the "android push configuration" and save configuration 5) add the ti.cloud and ti.cloudPush module in my app 6) use this code which is the example in the doc.

var CloudPush = require('ti.cloudpush');
CloudPush.retrieveDeviceToken({
    success: function deviceTokenSuccess(e) {
        Ti.API.info('Device Token: ' + e.deviceToken);
    },
    error: function deviceTokenError(e) {
        alert('Failed to register for push! ' + e.error);
    }
});

But when i run the app, the console show the above error. I searched in the forum, but the only answer is about an error during the "android push configuration" saving. I've tried to re-save all the setting, but nothing happen. Why? What am i doing wrong?

Thanks in advance