WPF Caliburn integration - Interaction issue

I'm working on a WPF application and I want to integrate Caliburn Micro. In the main page I have a content presenter which is loaded with a UserControl (let`s say is named MenuView as you can see below) when application starts. But when I try to handle a MouseDown event using interaction in MenuView, the method is never called in MenuViewModel, because probably the viewmodel is not registed in Caliburn.

Here is the application structure:

MainViewModel:

public class MainViewModel : PropertyChangedBase, IShell
{
    public MainViewModel()
    {
        SelectedView = new MenuView();
    }

    private UserControl _selectedView;
    public UserControl SelectedView
    {
        get { return _selectedView; }
        set
        {
            _selectedView = value;
            NotifyOfPropertyChange();
        }
    }
}

MainView:

<Window x:Class="UITablet.Views.MainView"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        Title="MainWindow" WindowState="Maximized" WindowStyle="ThreeDBorderWindow">
    <StackPanel VerticalAlignment="Bottom">   
        <ContentPresenter Content="{Binding SelectedView, Mode=TwoWay}" />
    </StackPanel>
</Window>

MenuViewModel:

public class MenuViewModel : IShell
{
    public void RedirectToSapAction()
    {
        //...
    }
}

MenuView:

<UserControl x:Class="UI.Tablet.Views.MenuView"
             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"
             xmlns:cal="http://www.caliburnproject.org"
             xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
             d:DesignHeight="300" d:DesignWidth="300">
    <Grid>
        <Button x:Name="TestButton" Width="100" Height="20" Content="Click me!">
            <i:Interaction.Triggers>
                <i:EventTrigger EventName="MouseDown">
                    <cal:ActionMessage MethodName="RedirectToSapAction" >
                    </cal:ActionMessage >
                </i:EventTrigger>

            </i:Interaction.Triggers>
        </Button>

    </Grid>
</UserControl>

And finally the AppBootstrapper

using System.IO;
using System.Linq;
using System.Reflection;
using WpfApplication1.ViewModels;
using System;
using System.Collections.Generic;
using Caliburn.Micro;

namespace WpfApplication1 
{
    public class AppBootstrapper : BootstrapperBase 
    {
        SimpleContainer container;

        public AppBootstrapper() 
        {
            Initialize();
        }

        protected override void Configure() 
        {

            ViewLocator.AddSubNamespaceMapping("WpfApplication1.ViewModels", "UITablet.Views");

            container = new SimpleContainer();

            container.Singleton<IWindowManager, WindowManager>();
            container.Singleton<IEventAggregator, EventAggregator>();
            container.PerRequest<IShell, MainViewModel>();
        }

        protected override object GetInstance(Type service, string key) {
            var instance = container.GetInstance(service, key);
            if (instance != null)
                return instance;

            throw new InvalidOperationException("Could not locate any instances.");
        }

        protected override IEnumerable<object> GetAllInstances(Type service) {
            return container.GetAllInstances(service);
        }

        protected override void BuildUp(object instance) {
            container.BuildUp(instance);
        }

        protected override void OnStartup(object sender, System.Windows.StartupEventArgs e) {
            DisplayRootViewFor<IShell>();
        }

        protected override IEnumerable<Assembly> SelectAssemblies()
        {
            var assemblies = new List<Assembly>();
            assemblies.AddRange(base.SelectAssemblies());
            //Load new ViewModels here
            string[] fileEntries = Directory.GetFiles(Directory.GetCurrentDirectory());

            assemblies.AddRange(from fileName in fileEntries where fileName.Contains("UITablet.dll") select Assembly.LoadFile(fileName));

            return assemblies;
        }
    }
}

As you can see, the views are placed in a separate project and I`ve done some tricks in order to make Caliburn functional. The question is, this separation is the problem? or am I missing something?

In your main view model, define a property of type MenuViewModel

private MenuViewModel_selectedView;
public MenuViewModel SelectedView
{
    get { return _selectedView; }
    set
    {
        _selectedView = value;
        NotifyOfPropertyChange();

    }
}

You can instantiate the SelectedView property in the constructor or whenever it's necessary.

In your view:

 <ContentPresenter cal:View.Model="{Binding SelectedView, Mode=TwoWay}">

        </ContentPresenter>