Not able to find object

Within your code, can you insert Sys.HighlightObject(Advancebutton)

    var Advancebutton = Action.FindChild(prop3, value3, 100);
    Sys.HighlightObject(Advancebutton);
    if (Advancebutton.WaitProperty("Exists", "true", 10000)) {
        Advancebutton.Click();
    } else {
        Log.Message("Diagnose button is not enabled")
    }

Is it highlighting the correct control?

Also, is it necessary to check for Exists? Can you not just do,

   var Advancebutton = Action.FindChild(prop3, value3, 100)
   if (Advancebutton.Exists)
      Advancebutton.Click();

Also, can you use the 'insert/edit code sample' button, and format your code

so it's makes it easier for us to read.