have you taken the parking break off?
Releasing the parking break releases the throttle above idle.
Might not be your issue, but also might contribute.
Startup sequence:
Turn on battery, gen and apu
Turn on fuel pumps, decs and fuel lever,
Engine startup, once engine RPM move throttle fwd to detent, engine spools up.
Release parking break, allowing throttle full movement.
There are other steps to become functional, but that should get the engines going.