Minimize / Maximize external application C++

Hello, I am trying to minimize / maximize / hide to system tray application which is built with Qt...

My code below works for example with Notepad, but it does not work with app built with Qt... Any idea how can I solve that problem?

My program find application built with Qt, but it does not minimize / maximize / hide it...

void Test1::test()
{

	HWND hwnd = FindWindow(NULL, L"Notepad");
	if (hwnd != 0)
	{
		ShowWindowAsync(hwnd, SW_MINIMIZE);
		ui.label->setText("Window found");
	}
	else
	{
		ui.label->setText("Window not found");
	}

}