The exact same thing is happening to my brother and I.
Whenever we try to do a cold start in any Multiplayer game the engines will not start.
We get all the way up to the point of moving the engines from OFF to IDLE and nothing works.
Remapping keys, etc nothing.
We load up a single player game, and get to the same point.
Hit LALT+HOME and RCTRL+HOME and it moves right off idle and spins up the engines without fail.
By the same token doing the Autostart never powers up the engines either.
It goes through as much as it can, but ultimately the engines never spool up.
Once again, only in multiplayer maps.