No ScrollBar in DataGrid and it's NOT in a Stack Panel

I have a DataGrid inside a Grid that will not display a vertical scroll bar when needed.  I've read many post re:this issue and tried lot's of solutions but nothing seems to fix this issue. Below is my XAML code.

Please advise.

<Grid Height="Auto" DataContext="{StaticResource aSIPsychProblemsViewSource}" Margin="100,60,0,0"><DataGrid x:Name="aSIPsychProbDataGrid" Height="Auto" AutoGenerateColumns="False" ItemsSource="{Binding}"
                                RowDetailsVisibilityMode="VisibleWhenSelected" ScrollViewer.VerticalScrollBarVisibility="Visible" ScrollViewer.CanContentScroll="True" FontSize="16" FontFamily="Century Gothic" HorizontalAlignment="Left"><DataGrid.Columns><DataGridTextColumn x:Name="clientNumberColumn" Binding="{Binding ClientNumber}" Header="Client Number" Width="SizeToHeader" Visibility="Collapsed"/><DataGridTextColumn x:Name="caseNumberColumn" Binding="{Binding CaseNumber}" Header="Case Number" Width="SizeToHeader" Visibility="Collapsed"/><DataGridTextColumn x:Name="followupColumn" Binding="{Binding Followup}" Header="Followup" Width="SizeToHeader" Visibility="Collapsed"/><DataGridComboBoxColumn SelectedValueBinding="{Binding PsychProblem}"
                                        ItemsSource="{Binding Source={StaticResource aSICodesPsychProbViewSource}}"
                                        DisplayMemberPath="PsychProblemDesc" SelectedValuePath="PsychProblem" MinWidth="120"
                                        Header="Problems" Width="SizeToCells"/><DataGridTextColumn Header="# days last 30" Width="SizeToHeader" Binding="{Binding Last30Days}" /><DataGridCheckBoxColumn Header="Ever experienced in lifetime?" Width="SizeToHeader" Binding="{Binding Lifetime}"/></DataGrid.Columns></DataGrid></Grid>