TextToSpeech.SpeakAsync from Xamarin.Essentials doesn't produce any sound

Hi,
I try the TextToSpeech.SpeakAsync feature, but it I gets no sound and no error is shown.
In addition, the row after the await is never reached.

private async void Button1_OnClicked(object sender, EventArgs e)
{
await TextToSpeech.SpeakAsync("Hi there");
int x = 9; //this row is never reached
}

P.S I use Android 6.0.1 The media and sounds level are on maximum.