Did the starter turn and the engine did not fire or did the starter not engage at all? The starter circuit goes through the neutral safety switch, if the NS switch doesn't close the starter won't engage. What year is the car? Hook a multimeter or a test light to the s terminal on the solenoid and see if there is 12 volts to the s terminal when the ignition switch is in the start position. Seems to be a lot of posts concerning starter not engaging with new harnesses lately.
