Try getting the valid handle of the window using attributes.
Also get the handle of the control by using AutoIT window info. The button class should be something like CLASS:WindowsForms10.BUTTON.app.0.378734a
and its instance should be also given (say 5). Then script looks like:
Local $hSecWnd=WinGetHandle("[CLASS:WindowsForms10.Window.8.app.0.378734a; W:1366; H:728]") ControlClick($hSecWnd,"","[CLASS:WindowsForms10.BUTTON.app.0.378734a; INSTANCE:5]")