Ajax Modal Popup Extender and Confirm Button Extender not working

I am trying to confirm a deletion in a repeater. I put the ajax controls in but when I click the delete button, I breakpoint in the repeater_ItemCommand without the popup panel being launched. I have similar code in another section for a gridview that works.

Here is the markup

<asp:Button ID="btnDeleteBlock" runat="server" Text="Delete Block" CommandArgument='<%# Eval("blockid") %>' CommandName="DeleteBlock" /><ajaxToolkit:ConfirmButtonExtender ID="ConfirmButtonExtender3" runat="server" TargetControlID="btnDeleteBlock" DisplayModalPopupID="MPE5_ConfirmDelete" /><ajaxToolkit:ModalPopupExtender ID="MPE5_ConfirmDelete" runat="server" OkControlID="btnYes"
                                                    CancelControlID="btnNo" PopupControlID="pnlTab5_ConfirmDelete" TargetControlID="btnDeleteBlock" DropShadow="true" /><asp:Panel ID="pnlTab5_ConfirmDelete" runat="server" CssClass="modalPopup" Height="100px" Width="300px" BorderWidth="1px" BorderColor="Black"><div style="padding: 5px;">
                                                        Confirmation</div><div style="padding: 5px;">
                                                        Do you want to delete this record?</div><div style="padding: 5px;"><asp:Button ID="btnYes" runat="server" Text="Yes" /><asp:Button ID="btnNo" runat="server" Text="No" /></div></asp:Panel>