Submit button doesn't fire when using a ValidationGroup

 My Submit button doesn't fire when using a ValidationGroup, but fires fire when I remove ValidationGroup on my button (ID="btnSend")
Code:
<asp:Panel ID="pnlRemindMe" runat="server" style="display: none;" CssClass="modalPopupReminder"> Please send an e-mail reminder for <br /> "<asp:Label ID="CourseTitleLabel" runat="server" Text='<%# Eval("CourseTitle") %>' Font-Bold="True" />" <br /> that starts on <asp:Label ID="StartDateLabel" runat="server" Text='<%# Eval("StartDate", " {0:MMMM dd, yyyy}") %>' /> <br /><br />     First Name: <asp:TextBox ID="firstName&quo ...