Hey Thomas, you may want to double check that the hwnd you are getting is the right one - those windows funcs would execute without an exception if they had some kind of error or problem.
Also, the normal way to get an hwnd in pygame is this:
hwnd = pygame.display.get_wm_info()['window']
So you might want to do a quick check to see if the value from the FindWindowA func matched what get_wm_info gives you.