Stylet MVVM binded VM don't show view - vb.net

Question

As the code showed below I have the main RootViewModel and View where I placed a Content Control, and binded it to ActiveItem. My iusse is that when clicking the button the RedView is not showed, instead is drawed the text StyletTest.RedViewModel.
I need to show the corresponding View in the content control when click a button(here reported only one view and view model to not be too long.) What am I missing?
here the code:
RootView and RootViewModel
<Window x:Class="RootView"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
xmlns:s="https://github.com/canton7/Stylet"
xmlns:local="clr-namespace:StyletTest"
xmlns:syncfusion="http://schemas.syncfusion.com/wpf"
mc:Ignorable="d"
Title="RootView"
Height="300" Width="300" >
<Grid>
<TextBlock>Hello, World</TextBlock>
<Button Command="{s:Action ShowA}" Margin="50,50,50,172" >Click me</Button>
<ContentControl Content="{Binding ActiveItem}" HorizontalAlignment="Left" Height="106" Margin="50,142,0,0" VerticalAlignment="Top" Width="185" />
</Grid>
</Window>
Imports Stylet
Public Class RootViewModel
Inherits Conductor(Of Object)
Private windowManager As IWindowManager
Public Sub New(ByVal windowManager As IWindowManager)
Me.windowManager = windowManager
End Sub
Public Sub ShowA()
Me.ActivateItem(New RedViewModel())
End Sub
End Class
the RedViewModel and RedView:
Imports Stylet
Public Class RedViewModel
Inherits screen
End Class
<UserControl x:Class="RedView"
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"
xmlns:local="clr-namespace:StyletTest"
xmlns:s="https://github.com/canton7/Stylet"
mc:Ignorable="d"
d:DesignHeight="450" d:DesignWidth="800">
<Grid Background="Red">
</Grid>
</UserControl>

Answer 1

The Content property is the wrong one to bind.