Game mode switcher does not work

When I try to use the game mode switcher it does not work at all. I tried spamming F3 + F4 but nothing happened. I tried holding F3 and F4 but nothing happened. I tried holding F3 first and then press F4 but nothing happened. I tried everything and nothing happens. Either the instructions in the F3+Q list are very unclear or it just doesn't work for me