AboutView not registered?

 protected override void OnStartup(StartupEventArgs e)
 {
     base.OnStartup(e);
     var serviceCollection = new ServiceCollection();
     ConfigureServices(serviceCollection);

     _serviceProvider = serviceCollection.BuildServiceProvider();

     var mainWindow = _serviceProvider.GetRequiredService<MainWindow>();

     mainWindow.Show();
 }

 private void OnExit(object sender, ExitEventArgs e)
 {
     // Dispose of services as needed
     if (_serviceProvider is IDisposable disposable)
     {
         disposable.Dispose();
     }
 }

 private void ConfigureServices(IServiceCollection services)
 {
     // Configure logging
     services.AddLogging();

     // Register Views
     services.AddSingleton<MainWindow>();
     services.AddSingleton<AboutView>();

     // Register ViewModels
     services.AddSingleton<IMainWindowViewModel, MainWindowViewModel>();
     services.AddSingleton<IAboutViewViewModel, AboutViewViewModel>();

     // Register Services
     services.AddSingleton<IFileDialog, FileDialog>();
     services.AddSingleton<ILogger, Logger>();
 }