When advancing the throttle to start the engine are you pressing the button to disengage the shift cable so that the neutral safety switch stays closed?
What year and shifter do you have?
Not clear what the problem is, does it not crank or crank but hard to start?
1997 Silverton 362, 7.4 Crusaders
1997 2400 SCR, 5.7 Vortec / Bravo 2