EventHandler not triggering when checkbox checked

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C#

ASP.NET

When I check the checkbox, the code is not reaching the event handler. I verified this by giving
a break point. Hereunder is my code:

<asp:CheckBox ID="GuestChkBox" runat="server" OnCheckedChanged="CheckBox1_CheckedChanged" style=" margin-top:78px;margin-left:600px; font-size:larger"
 ></asp:CheckBox>

protected void CheckBox1_CheckedChanged(Object sender, EventArgs e)
    {
    }