@pier74 This is an answer direct from the developer for you.
If you're following the checklists... it could be that there's no fuel in the aircraft. Asobo resets the fuel to zero sometimes when you reload aircraft. It could be that you're using external hardware or events that incorrectly set the fuel selectors, such as to "LEFT", instead of "LEFT MAIN". Are you sure you're positioning the starter switch to "START", and not "MOTOR"? For this, check to see if the green annunciator "IGNITION ON" is illuminated while starting.
Hope this helps.