Prism 7: Can’t display view - wpf

Question

I'm trying to display a view with prism region manager. The problem is that Views are added to the RegionManager and ActiveViews is set but nothing is displaying in MainView(StartWindowView).
My Bootstrapper:
public class Bootstrapper: UnityBootstrapper
{
private readonly Action<Window> aR;
public Bootstrapper(Action<Window> AR)
{
aR = AR;
}
protected override DependencyObject CreateShell()
{
return Container.TryResolve<Views.StartWindowView>();
}
protected override void InitializeShell()
{
aR(Container.TryResolve<Views.StartWindowView>());
}
protected override void ConfigureContainer()
{
base.ConfigureContainer();
Container.RegisterType(typeof(object), typeof(Views.TestView),"PlotListView");
Container.RegisterType(typeof(object), typeof(Views.SettingsView), "SettingsView");
Container.RegisterType<IAutoCadService, AutoCadService>
(new ExternallyControlledLifetimeManager());
Container.RegisterType<IPlotListViewModel, PlotListViewModel>
(new ExternallyControlledLifetimeManager());
}
}
My MainWindow(StartWindowView) with RegionManager.RegionName="ContentRegion":
Window x:Class="PlottingFastAutoCAD2016.Views.StartWindowView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
mc:Ignorable="d"
Background="LightSkyBlue"
x:Name="window"
xmlns:res="clr-namespace:PlottingFastAutoCAD2016.ViewModels"
d:DataContext="{x:Static res:StartWindowViewModelDesign.Instanc}"
xmlns:prism="http://prismlibrary.com/"
prism:ViewModelLocator.AutoWireViewModel="True"
ResizeMode="NoResize"
SizeToContent="WidthAndHeight"
d:DesignHeight="500"
d:DesignWidth="600">
<Grid >
<Grid.RowDefinitions>
<RowDefinition Height="auto"/>
<RowDefinition Height="*"/>
<RowDefinition Height="*"/>
</Grid.RowDefinitions>
<Grid Grid.Row="0">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"/>
<ColumnDefinition Width="auto"/>
</Grid.ColumnDefinitions>
<Button Width="50"
Grid.Column="0"
Padding="0"
HorizontalAlignment="Left"
BorderThickness="0"
Height="Auto"
Click="Button_Click"
Command="{Binding ElementName=window,
Path=DataContext.NavigationCommand}"
CommandParameter="PlotListView"
Background="Transparent">
<StackPanel VerticalAlignment="Stretch"
Margin="3">
<Image Stretch="Fill"
Source="/PlottingFastAutoCAD2016;component/Resources/Icon/printer-.png"/>
<TextBlock Text="Plot"
HorizontalAlignment="Center"
Foreground="White"/>
</StackPanel>
</Button>
<Button Width="50"
Grid.Column="1"
Padding="0"
BorderThickness="0"
Height="Auto"
Command="{Binding ElementName=window,
Path=DataContext.NavigationCommand}"
CommandParameter="SettingsView"
Background="Transparent">
<StackPanel VerticalAlignment="Stretch"
Margin="3">
<Image Stretch="Fill"
Source="/PlottingFastAutoCAD2016;component/Resources/Icon/settings.png"/>
<TextBlock Text="Settings"
HorizontalAlignment="Center"
Foreground="White"/>
</StackPanel>
</Button>
</Grid>
<ItemsControl prism:RegionManager.RegionName="ContentRegion"
Grid.Row="1"
x:Name="contentRegion"
/>
</Grid>
</Window>
My ModelView:
public class StartWindowViewModel : BindableBase, IStartWindowViewModel
{
private readonly IRegionManager regionManager;
public StartWindowViewModel(IRegionManager regionManager)
{
this.regionManager = regionManager;
NavigationCommand = new DelegateCommand<string>(Navigate);
}
private void Navigate(string uri)
{
regionManager.RequestNavigate("ContentRegion", new Uri(uri, UriKind.Relative),
r => {
if (r != null) ;
//MessageBox.Show("Result: "+r.Result);
else MessageBox.Show("Error: " + r.Error.Message);
});
}
public DelegateCommand<string> NavigationCommand { get; set; }
}
Anyone have idea what is going on? I have spent three days to resolve it but no luck.