I'm not with Laminar Research, just a fellow simmer from the UK.
I've just launched X-Plane 11 and loaded the default Cessna 172 and using the mouse, I did the following:-
1. Turn on both master switches
2. Turn on both avionics switches
3. Set mixture to full
4. Set throttle to fast idle
5. Turned the ignition key...…… and the engine fired up without any difficulty.
Are you saying that in your version of X-Plane 11, you cannot do any of this?