Vertical bar is not doing anything in a DataGrid in WPF

Question

I am trying to discover why my vertical scrollbar is not doing anything. I can actually see a scrollbar when I set the VerticalScrollBarVisibility = True. But it doesn't do anything. I am new to designing WPF and scrollbars are one of the hardest to understand.

<Grid>
    <StackPanel>
        <materialDesign:Card Padding="32" Margin="16">
            <TextBlock Style="{DynamicResource MaterialDesignTitleTextBlock}">UNREAD TAG REPORTER</TextBlock>
        </materialDesign:Card>

        <materialDesign:Card Margin="16 5">
            <Grid>
                <Grid.RowDefinitions>
                    <!--Row1-->
                    <RowDefinition Height="Auto" />
                    <!--Row2-->
                    <RowDefinition Height="*" />
                </Grid.RowDefinitions>
                <!--Row1 Column1-->
                <Grid Grid.Row="0">
                    <StackPanel Orientation="Horizontal">
                        <Label Content="Date From: " Margin="5 10 0 10"/>
                        <DatePicker Width="100" x:Name="DateFrom" />

                        <Label Content="Date To: " Margin="5 10 0 10" />
                        <DatePicker Width="100" x:Name="DateTo" />

                        <Label Content="Plaza: " Margin="25 10 0 10" />
                        <TextBox Width="50" x:Name="TxtPlaza" Text="801" Margin="5 10 0 10"/>

                        <Label Content="Lane: " Margin="10 10 0 10" />
                        <TextBox Width="50" x:Name="TxtLane" Margin="5 10 0 10" Text="4"/>

                        <Button Content="Get Values" Margin="30 0 0 0" x:Name="BtnPopulateGrid" />
                    </StackPanel>

                </Grid>
            </Grid>
        </materialDesign:Card>

        <materialDesign:Card Margin="16 5">
            <Grid>
                <Grid.RowDefinitions>
                    <!--Row1-->
                    <RowDefinition Height="Auto" />
                    <!--Row2-->
                    <RowDefinition Height="Auto" />
                </Grid.RowDefinitions>
                <!--Row1 Column1-->
                <Grid Grid.Row="0">
                    <StackPanel Orientation="Horizontal">
                        <Button Content="Get Manual Count" 
                                Margin="20 10" 
                                x:Name="BtnGEtManualCount" 
                                Click="BtnGEtManualCount_OnClick"/>
                    </StackPanel>

                </Grid>
            </Grid>
        </materialDesign:Card>

        <Grid>
            <Grid.RowDefinitions>
                <RowDefinition Height="*" />
            </Grid.RowDefinitions>
            <DataGrid  ColumnWidth="*" 
                       x:Name="ViewingGrid"
                       VerticalScrollBarVisibility="Auto" 
                       HorizontalScrollBarVisibility="Auto" 
                       Margin="10,0,27,0" />

        </Grid>
    </StackPanel>
</Grid>