[Solved] CheckBox change event inside ASP.Net GridView not firing in second Click

Delete function not working if check box is unchecked so the alert message not poping up when the checkbox is unchecked .

Database Structure

CREATE TABLE [dbo].[order]( [id] [int] IDENTITY(1,1) NOT NULL, [accepted] [nvarchar](255) NULL, ) ON [PRIMARY] GO

CREATE TABLE [dbo].[Tracking]( [id] [int] IDENTITY(1,1) NOT NULL, [cylinderid] [nvarchar](255) NULL, [cylinderno] [nvarchar](255) NULL ) ON [PRIMARY] GO

<asp:GridView ID="gvDetails" runat="server" AutoGenerateColumns="False" BackColor="White" BorderColor="#3366CC" BorderStyle="None"
    Font-Names="Century Gothic" Font-Size="x-Small" DataKeyNames="id" Width="38%" Style="margin-bottom: 0px" CssClass="grid">
    <Columns>
        <asp:TemplateField>
            <ItemTemplate>
                <asp:CheckBox ID="chkSelect" runat="server" OnCheckedChanged="OnChckedChanged" Text="Add" AutoPostBack="True" EnableViewState="False" />
            </ItemTemplate>
        </asp:TemplateField>
        <asp:BoundField DataField="id" HeaderText="id" />
        <asp:BoundField DataField="accepted" HeaderText="Cylinder No" />
    </Columns>
    <FooterStyle BackColor="White" ForeColor="#000066" />
    <HeaderStyle BackColor="#7EA9D3" Font-Bold="True" ForeColor="White" />
    <PagerStyle BackColor="White" ForeColor="#000066" HorizontalAlign="Left" />
    <RowStyle ForeColor="#000000" />
    <SelectedRowStyle BackColor="#669999" Font-Bold="True" ForeColor="#000000" />
    <SortedAscendingCellStyle BackColor="#F1F1F1" />
    <SortedAscendingHeaderStyle BackColor="#007DBB" />
    <SortedDescendingCellStyle BackColor="#CAC9C9" />
    <SortedDescendingHeaderStyle BackColor="#00547E" />
</asp:GridView>

protected void Page_Load(object sender, EventArgs e)
{
    if (!IsPostBack)
    {
        BindUserDetails();
    }
}
protected void BindUserDetails()
{
    string constr = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constr))
    {
        using (SqlDataAdapter sda = new SqlDataAdapter("Select id,purchaseorderno, accepted from orders ORDER BY id DESC", con))
        {
            using (DataTable dt = new DataTable())
            {
                sda.Fill(dt);
                gvDetails.DataSource = dt;
                gvDetails.DataSource = dt;
                gvDetails.DataBind();
            }
        }
    }

    //Required for jQuery DataTables to work.
    gvDetails.UseAccessibleHeader = true;
    gvDetails.HeaderRow.TableSection = TableRowSection.TableHeader;
}
protected void OnChckedChanged(object sender, EventArgs e)
{
    CheckBox chk = (CheckBox)sender;
    GridViewRow row = (GridViewRow)chk.NamingContainer;
    string id = row.Cells[1].Text;
    string number = row.Cells[2].Text;

    string constring = ConfigurationManager.ConnectionStrings["constr"].ConnectionString;
    using (SqlConnection con = new SqlConnection(constring))
    {
        if (chk.Checked)
        {
            using (SqlCommand cmd = new SqlCommand("INSERT INTO Tracking VALUES(@Id, @CylinderNo)", con))
            {
                cmd.Parameters.AddWithValue("@Id", id);
                cmd.Parameters.AddWithValue("@CylinderNo", number);
                con.Open();
                cmd.ExecuteNonQuery();
                con.Close();
            }
            ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record Inserted successfully.')", true);
        }
        else
        {
            using (SqlCommand cmd = new SqlCommand("DELETE FROM Tracking WHERE cylinderid = @Id", con))
            {
                cmd.Parameters.AddWithValue("@Id", id);
                con.Open();
                cmd.ExecuteNonQuery();
                con.Close();

            }
            ScriptManager.RegisterClientScriptBlock(this, this.GetType(), "alertMessage", "alert('Record Deleted successfully')", true);

        }
    }
}