WPF controls not showing even make it visible

Question

I encounter a problem that I am not sure how to fix. I have "AddAccount" (Button), "AccountsTextBlock" and a ListBox on the main window. If not user is added, the list box will be hidden, once user is added, it will show the ListBox, AddAccount and AccountsTextBlock on the same screen, but AddAccount and AccountsTextBlock will be at different positions from when there's no user. The problem is that AddAccount and AccountsTextBlock didn't show, but a dotted rectangle shows.

<Grid>
    <Canvas>
        <TextBlock x:Name="AddAccountTextBlock" HorizontalAlignment="Left" TextWrapping="Wrap" VerticalAlignment="Top" Height="60" Width="369" Text="Add account to allow for simple access to your company resources&#xD;&#xA;" SnapsToDevicePixels="True" Canvas.Left="38" Canvas.Top="313"/>
        <Button x:Name="AddAccount" Content="Add Account" Canvas.Left="145" Canvas.Top="333" HorizontalAlignment="Left" VerticalAlignment="Top" Width="140" RenderTransformOrigin="0.466,0.977" IsCancel="True" Height="40" Foreground="White" Background="Blue" Click="OnAddAccount"/>
        <TextBlock x:Name="AccountsTextBlock" Canvas.Left="176" TextWrapping="Wrap" Text="Accounts" Canvas.Top="10" Height="33" Width="68" FontSize="16" FontFamily="Tahoma"/>
    </Canvas>
    <ListBox x:Name="accounts" HorizontalAlignment="Left" Height="237" VerticalAlignment="Top" Width="444" SelectionChanged="ListBox_SelectionChanged" Background="White" BorderBrush="White" Margin="0,47,0,0" RenderTransformOrigin="0.5,0.5">
        <ListBox.RenderTransform>
            <TransformGroup>
                <ScaleTransform/>
                <SkewTransform AngleX="0.384"/>
                <RotateTransform/>
                <TranslateTransform X="-0.794"/>
            </TransformGroup>
        </ListBox.RenderTransform>
        <ListBox.ItemContainerStyle>
            <Style TargetType="ListBoxItem">
                <Setter Property="Height" Value="100"/>
                <Setter Property="Template">
                    <Setter.Value>
                        <ControlTemplate TargetType="ListBoxItem">
                            <Border Name="_Border" BorderBrush="Gray" BorderThickness="0.5"
                            Padding="2"
                            SnapsToDevicePixels="true">
                                <ContentPresenter />
                            </Border>
                            <ControlTemplate.Triggers>
                                <Trigger Property="IsSelected" Value="true">
                                    <Setter TargetName="_Border" Property="Background" Value="LightSkyBlue"/>
                                </Trigger>
                            </ControlTemplate.Triggers>
                        </ControlTemplate>
                    </Setter.Value>
                </Setter>
            </Style>
        </ListBox.ItemContainerStyle>
        <ListBox.ItemTemplate>
            <DataTemplate>
                <Grid Margin="3">
                    <Grid.ColumnDefinitions>
                        <ColumnDefinition Width="100"/>
                        <ColumnDefinition Width="*" />
                    </Grid.ColumnDefinitions>
                    <Image HorizontalAlignment="Left" VerticalAlignment="Center" Grid.Row="0" Grid.Column="0" Width="100" Source="{Binding Path=imagePath}" />
                    <TextBlock HorizontalAlignment="Center" VerticalAlignment="Center" Grid.Row="0" Grid.Column="1" Text="{Binding Path=userInfo}"></TextBlock>
                </Grid>
            </DataTemplate>
        </ListBox.ItemTemplate>
    </ListBox>
</Grid>

public MainWindow()
{
    InitializeComponent();

    using (RegistryKey key = Registry.CurrentUser.CreateSubKey(authenticatorRegistryKey))
    {
        Object valueStr = Registry.GetValue(authenticatorRegistryKey, addedUsersRegistryValueName, null);
        if (valueStr == null)
        {
            //no users added yet, hide list box and move add button
            accounts.Visibility = Visibility.Collapsed;
            AccountsTextBlock.Visibility = Visibility.Collapsed;
            Canvas.SetLeft(AddAccountTextBlock, (Application.Current.MainWindow.Width - AddAccountTextBlock.Width) / 2);
            Canvas.SetTop(AddAccountTextBlock, (Application.Current.MainWindow.Height - AddAccountTextBlock.Height) / 2 - AddAccount.Height + 10);
            Canvas.SetLeft(AddAccount, (Application.Current.MainWindow.Width - AddAccount.Width) / 2);
            Canvas.SetTop(AddAccount, (Application.Current.MainWindow.Height - AddAccount.Height) / 2);
        }
        else
        {
            //show the added user
            List<UserInfo> items = new List<UserInfo>();
            items.Add(new UserInfo()
            {
                userInfo = "abcdefg",
                imagePath = ""
            });

            accounts.ItemsSource = items;
            AccountsTextBlock.Visibility = Visibility.Visible;
            accounts.Visibility = Visibility.Visible;
        }
    }
}

private void OnAddAccount(object sender, RoutedEventArgs e)
{

    SignInUrlWindow signInUrlWindow = new SignInUrlWindow();
    signInUrlWindow.Left = Application.Current.MainWindow.Left;
    signInUrlWindow.Top = Application.Current.MainWindow.Top;
    signInUrlWindow.Width = Application.Current.MainWindow.Width;
    signInUrlWindow.Height = Application.Current.MainWindow.Height;
    signInUrlWindow.ShowDialog();

    List<UserInfo> items = new List<UserInfo>();
    items.Add(new UserInfo()
    {
        userInfo = "abcdefg",
        imagePath = ""
    });

    accounts.ItemsSource = items;

    accounts.Visibility = Visibility.Visible;
    AddAccount.Visibility = Visibility.Visible;
    AccountsTextBlock.Visibility = Visibility.Visible;
}