I have a few planes that won't throttle up with either the joystick or keyboard command.  They did work at one time then quit.  I thought it was the throttle on the jstick but it worked fine in calibration and in other sims.  Then I noticed that most of the planes worked fine.

Jim

Try using the engine select sequence.

To select all engines, press e then 1 then 2 then 3 then 4 in rapid order (depending on the number of engines). Each number represents one engine from port to starboard.

For manual start-up/shut-down you can select individual engine by pressing e then 'engine number'.

Remember to do the e-1-2-3-4 after manual start-up.

You might check your default flight to see if it has only one engine selected at 'fly now'. Maybe this could carry over to any multi-engine a/c in 'create a flight'.

Cheers,
Dave