Listview does not slide

In a Listview I am adding elements, but when there are more elements that the screen allows to display, it does not scroll .

Solution: The error was in the IsEnabled property, I wanted the photos could not be selected but I had not realized that I was also disabling the Scroll.

Here the view:

<ContentPage.Content>
    <StackLayout
            Margin="10"
            BindingContext="{Binding DatosBase}">
        <Button 
              Command="{Binding TakePictureCommand}" 
              Text="Tomar Foto" />
        <ListView
                x:Name="Fotos"
                IsEnabled="False"
                ItemsSource="{Binding Imagenes}"
                HasUnevenRows="True">
            <ListView.ItemTemplate>
                <DataTemplate>
                    <ViewCell>
                        <Grid Margin="5">
                            <Grid.RowDefinitions>
                               <RowDefinition Height="150" />
                            </Grid.RowDefinitions>
                            <Image
                               WidthRequest="150"
                               HeightRequest="150"
                               Source="{Binding Image}" />
                        </Grid>
                    </ViewCell>
                </DataTemplate>
            </ListView.ItemTemplate>
        </ListView>
    </StackLayout>
</ContentPage.Content>

Thanks for your help.