Bluetooth Xamarin Forms

Hi, i have a problem using xamarin forms to android.

Im trying to list all devices to connect using Robotics Component.

The adapter is comming as well
adapter.StartScanningForDevices ();

but this event is not fired when discover a device

adapter.DeviceDiscovered += (object sender, DeviceDiscoveredEventArgs e) => {
Device.BeginInvokeOnMainThread(() => {
teste.Text= "Discovered a device";
});
};

I receive no one erros, but the event is not fired..
Yes, the manifest is OK, i have enabled the blueooth permissions.

Do you guys know why?