Community.Toolkit.MVVM Error on [ObservableProperty]: The name 'x' does not exist in current context

[ObservableProperty]
bool _authenticated = false;

[ObservableProperty]
bool _authenticated = false;

<UserControl.DataContext>
    <viewmodels:MainViewModel x:Name="MainViewModel"/>
</UserControl.DataContext>

<UserControl.DataContext>
    <viewmodels:MainViewModel x:Name="MainViewModel"/>
</UserControl.DataContext>

public MainViewModel()
{
    userSettings = UserSettings.Instance;
    gitClient = new GitService(userSettings);
    TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
}

[RelayCommand(FlowExceptionsToTaskScheduler = true)]
private async Task AuthenticateUserAsync()
{
    this.Authenticated = await gitClient.AuthenticateUserAsync();
}

 private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
 {
     ExceptionMessageText = e.Exception.Message;
 }

public MainViewModel()
{
    userSettings = UserSettings.Instance;
    gitClient = new GitService(userSettings);
    TaskScheduler.UnobservedTaskException += TaskScheduler_UnobservedTaskException;
}

[RelayCommand(FlowExceptionsToTaskScheduler = true)]
private async Task AuthenticateUserAsync()
{
    this.Authenticated = await gitClient.AuthenticateUserAsync();
}

 private void TaskScheduler_UnobservedTaskException(object sender, UnobservedTaskExceptionEventArgs e)
 {
     ExceptionMessageText = e.Exception.Message;
 }

[RelayCommand]
private async Task AuthenticateUserAsync()
{
    this.Authenticated = await gitClient.AuthenticateUserAsync();
}

[RelayCommand]
private async Task AuthenticateUserAsync()
{
    this.Authenticated = await gitClient.AuthenticateUserAsync();
}

[RelayCommand]
private async Task AuthenticateUserAsync()
{
   await gitClient.AuthenticateUserAsync();
}

[RelayCommand]
private async Task AuthenticateUserAsync()
{
   await gitClient.AuthenticateUserAsync();
}