Why my button doesn't do a postback?

Hi experts!
I've a Web User Control that contain a "Panel" inside this panel there is a button.The button have an event in the server side called Button1_Click.

Also I've a page, in which I am calling a Collapsible panel Extender from the server side.One of the properties of this Collapsible panel Extender is to have a TargetControlID, this TargetControlID need to be a "Panel".  I am targetting the "Panel" from my Web User Control. This work fine and show the panel...BUT

The button inside the panel have lost the event. The event Button_click is not trigerring at all....
WHY?????.....I am attaching my code with comments
Thanks

Ps: So far I have publish a question like this for 3 days and nobody have found an answer.....

This is the web user control .ascx
<%@ Control Language="C#" AutoEventWireup="true" CodeFile="Exampletry.ascx.cs" Inherits="controls_Exampletry" %>
 
<asp:Panel ID="ContentPanelStep" runat="server">   // the panel which it is going to be the TargetID for the collapsiblePanel
 
   <asp:Button ID="Button1" runat="server" Text="Testing" OnClick="Button1_Click" />       //The button  is inside the Panel with an event, this button is the one that is triggering.
 
</asp:Panel>
 
This is the web user control ascx.cs:
public partial class controls_Exampletry : System.Web.UI.UserControl
{
    protected void Page_Load(object sender, EventArgs e)
    {
 
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
              //This is the event that is not triggering
    }
 
    public Panel StepPanel
    {
        get { return ContentPanelStep; }  //this is my panel and inside this panel there is a button. I make it public so I can call it for the aspx. page
    }
}
 
 
This is my code in my page:
    protected void Page_Load(object sender, EventArgs e)
    {        
     controls_Exampletry myControl = (controls_Exampletry)Page.LoadControl("controls/Exampletry.ascx");  //Loading hte WebUserControl into am object called mycontrol
      myControl.ID= = "MyControl1"; //Seting and ID for this object
      HtmlTableRow stepRow = new HtmlTableRow();      //This is a dynamic Row
      HtmlTableCell stepCell = new HtmlTableCell();        //This is a dynamic Cell
     AjaxControlToolkit.CollapsiblePanelExtender cpe1 = new AjaxControlToolkit.CollapsiblePanelExtender();    //creating the Collapsible Panel from server side and give it an instance or object
     
     cpe1.ID = "CollapsiblePanelExtender";   // giving an ID to the Collapsible Panel
     cpe1.TargetControlID = myControl.StepPanel.UniqueID;
                     //This is the line that I think is the problem, I am callling the ID for the panel that is contained in the web  user control . I tried ClientID and it didn't work neither. I can see the panel with the button but the event from that button inside that panel is not triggering.  
        stepCell.Controls.Add(myControl);
        stepCell.Controls.Add(cpe1);
        stepRow.Cells.Add(stepCell);
        StepsTable.Rows.Add(stepRow);      //I have a table with ID=StepsTable that will received this adding of the row
    }

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