Monogame, Xbox One, and the Creator's Program

OK so I have tried a few different bits of code based on what has been kindly provided on this forum but I still cannot get the sign in to work. I have kept the following code very very simple to demonstrate the point it is breaking down

private async void GetUser()
{
SignInResult signInSilentlyTask;
SignInResult signInLoudlyTask;
user = new XboxLiveUser();
debug = “”;

        var dispatcher = Windows.ApplicationModel.Core.CoreApplication.MainView.CoreWindow.Dispatcher;
        signInSilentlyTask = await user.SignInSilentlyAsync(null);
        if (signInSilentlyTask.Status == SignInStatus.Success)
        {
            debug += "Worked ";
        }
        else
        {
            debug += signInSilentlyTask.Status.ToString();
        }
        if (signInSilentlyTask.Status == SignInStatus.UserInteractionRequired)
        {
            signInLoudlyTask = await user.SignInAsync(null); // **Error here**
            debug += signInLoudlyTask.Status.ToString();
        }
        debug += " exit";

}

When I try user.SignInAsync(null); or user.SignInAsync(dispatcher); I get an error
System.InvalidOperationException ‘Operation is not valid due to the current state of the object’

System.InvalidOperationException occurred
HResult=0x80131509
Message=Operation is not valid due to the current state of the object.
Source=
StackTrace:
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
at CatStack.Game1.d__163.MoveNext() in C:\Users\xx\source\repos\CatStack\CatStack\Game1.cs:line 561

I have tried different combinations, null, dispatcher, two dispatcher objects, .CoreApplication.GetCurrentView() instead of .CoreApplication.MainView, try / catch statements. Nothing seems to work. I get the same error message

I am signed into my sandbox with a valid user. I can see my profile when I launch the game and press the XBox home button

But I cannot seem to be able to get the signed in user or force a sign in

Your help will be much appreciated