TextToSpeech plugin not working on Android

Hi,

I'm trying to get the TextToSpeech plugin working but when I call CrossTextToSpeech.Current.Speak("Say something"); I'm getting the following error:-
System.NotImplementedException: This functionality is not implemented in the portable version of this assembly. You should reference the Xam.Plugins.TextToSpeech NuGet package from your main application project in order to reference the platform-specific implementation.

I've tried adding the nugget package using both the package manager and the package manager console. It looks like the references are getting added but I'm still getting these problems on my Android device. This works fine in the UWP app.

Any ideas?

Thanks,

Geoff