Sorting on RadGrid not working properly

Hello 

I am using RadGrid for sorting, filtering and paging. I have a problem with sorting, it doesn;t sort ascending, it simply ignores it. I don't want to use AllowNaturalSort property to False, i want all 3 sorting modes to work. I think i am missing a tag or something in RadGrid, but i can;t figure it out which one. Can u help me?

//sortcomand method

 protected void RadGrid1_SortCommand(object source, Telerik.Web.UI.GridSortCommandEventArgs e)
    {
         if (!e.Item.OwnerTableView.SortExpressions.ContainsExpression(e.SortExpression))
                {
                    GridSortExpression sortExpr = new GridSortExpression();
                    sortExpr.FieldName = e.SortExpression;
                    sortExpr.SortOrder = GridSortOrder.Ascending;
 
                    e.Item.OwnerTableView.SortExpressions.AddSortExpression(sortExpr);
                }
    }

//grid

  <telerik:RadAjaxManager ID="RadAjaxManager1" runat="server" UpdateInitiatorPanelsOnly="true">
        <AjaxSettings>
            <telerik:AjaxSetting AjaxControlID="RadGrid1">
                <UpdatedControls>
                    <telerik:AjaxUpdatedControl ControlID="RadGrid1" LoadingPanelID="RadAjaxLoadingPanel1" />
                </UpdatedControls>
            </telerik:AjaxSetting>
        </AjaxSettings>
    </telerik:RadAjaxManager>
    <telerik:RadAjaxLoadingPanel ID="RadAjaxLoadingPanel1" runat="server">
    </telerik:RadAjaxLoadingPanel>
     <telerik:RadGrid ID="RadGrid1" runat="server" AllowPaging="true"
        AllowSorting="True" GridLines="None" AutoGenerateColumns="False" OnSortCommand="RadGrid1_SortCommand"  OnNeedDataSource="RadGrid1_NeedDataSource">
      <MasterTableView AllowMultiColumnSorting="true">
           <Columns>
                <telerik:GridBoundColumn SortExpression="IovationDeviceID" HeaderText="Iovation Device ID" HeaderButtonType="TextButton"
                    DataField="IovationDeviceID">
                </telerik:GridBoundColumn>
                <telerik:GridBoundColumn SortExpression="IovationDeviceStatus" HeaderText="Iovation Result" HeaderButtonType="TextButton"
                    DataField="IovationDeviceStatus">
                </telerik:GridBoundColumn>
                <telerik:GridBoundColumn SortExpression="EventType" HeaderText="Integration Point" HeaderButtonType="TextButton"
                    DataField="EventType">
                </telerik:GridBoundColumn>
                <telerik:GridBoundColumn SortExpression="Ins" HeaderText="Timestamp" HeaderButtonType="TextButton"
                    DataField="Ins">
                </telerik:GridBoundColumn>
            </Columns>
        </MasterTableView>
        <PagerStyle AlwaysVisible="true" />
    </telerik:RadGrid>