Spy++ didnt show the button.

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C#2.0

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C#7.1

i am trying to control an application from c# application . i used spy++ to navigate the button .but it doesnot work for all buttons. how to solve it?

What I have tried:

private void button12_Click(object sender, EventArgs e)
      {
          IntPtr maindHwnd = FindWindow(null, "Inspector");
          if (maindHwnd != IntPtr.Zero)
          {
              //IntPtr panel = FindWindowEx(maindHwnd, IntPtr.Zero, "TPanel", null);
              IntPtr childHwnd = FindWindowEx(maindHwnd, IntPtr.Zero, " TPanel", "Connect");
              if (childHwnd != IntPtr.Zero)
              {
                  SendMessage(childHwnd, BM_CLICK, IntPtr.Zero, IntPtr.Zero);     // Send a message from the button
              }
              else
              {
                  textBox3.BackColor = Color.Yellow;
                  textBox3.Text = "エラー";
              }
          }
          else
          {
              textBox3.BackColor = Color.Yellow;
              textBox3.Text = "エラーメッセージボックスありません";
          }
      }