Telerik RadDate TimePicker is not working after ScriptManager.RegisterStartupScript

 Telerik RadDateTimePicker is not working after i register script using ScriptManager.RegisterStartupScript in C# code

Code :  ScriptManager.RegisterStartupScript(Page, typeof(Page), "mykey", "showSummaryPopup('TEst Message')", true);

 <telerik:RadDateTimePicker id="txtSendingScheduleDate" runat="server" skin="Vista" EnableAjaxSkinRendering="true" EnableViewState="true" 
            dateinput-readonly="false" />