Couple of things.
If your battery is dead, flaps, etc won't work as they should. You have a limited time in which to start the aircraft before the battery drains. If this is the case, simply reload the aircraft.
Secondly, you might have to prime the aircraft before starting.
Third, and it sounds like you accomplished all of this, ensure mixture is full rich, master battery is on, etc, prime then start.
From what I can tell, it sounds like your battery simply went dead.
That was the case... I guess I was taking to long to get the cockpit set up after turning the BAT and GEN switches on!!!