常规表达错误消息未显示.net

Question

我的reqular表达式不起作用但错误没有弹出
这是我的简短代码 - 看起来很简单，我无法弄清楚代码中的错误。

<TR id="ROW2" runat="server" visible="false">
    <TD class="main" align=left>
        <asp:Label id="Lab3" runat="server" Text="Cheque No: "></asp:Label>
    </TD>
    <TD vAlign=top align=left>
        <asp:TextBox id="TxtChequeno" runat="server" MaxLength="20" cssclass="textbox"></asp:TextBox>
        <asp:RegularExpressionValidator style="VERTICAL-ALIGN: top" id="REVMobile" runat="server" 
         ControlToValidate="TxtChequeno" 
         ErrorMessage="Please enter valid Cheque number" 
         ValidationExpression="^(?=.*\d).{10}$" 
         ValidationGroup="tripSheet">*</asp:RegularExpressionValidator>
    </TD>
</TR>
<TR id="ROW3" runat="server" visible="false">
    <TD class="main" align=left>
        <asp:Label id="Lab4" runat="server" Text="Cheque Date: "></asp:Label>
    </TD>
    <TD vAlign=top align=left>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
        <asp:TextBox id="txtFromDate" runat="server" CssClass="textbox" MaxLength="11" Width="128px"></asp:TextBox>
        <asp:Image style="CURSOR: pointer" id="ImaArr1" runat="server" ImageUrl="./images/CAL.GIF"></asp:Image>
        <cc1:CalendarExtender id="CalendarExtender2" runat="server" CssClass="yui" TargetControlID="TxtCardDte" PopupButtonID="ImaArr1" Format="dd-MMM-yyyy"></cc1:CalendarExtender>
        <asp:RequiredFieldValidator id="RFtxtFromDate" runat="server" ControlToValidate="txtFromDate" ErrorMessage="Select Arrival date" SetFocusOnError="True" ValidationGroup="tripSheet">*</asp:RequiredFieldValidator>
        <asp:CustomValidator ID="CustxtFromDate" runat="server" ClientValidationFunction="CallDateFunForToDate1" ControlToValidate="txtFromDate" ValidationGroup="tripSheet" errormessage="Invalid Cheque Date." style="vertical-align:top;">*</asp:CustomValidator>
    </td>
    </TD>
</TR>
<TR id="RowBtn" runat="server" visible="false">
    <td>
        <asp:Button ID="BtnAdd" runat="server" Text="Add" CssClass="button" ValidationGroup="tripSheet" />
    </td>
</TR>