Did you try adjusting the shifter cable at the transmission? Also when replying send me VIN# XXXXX I know which transmission you have to help diagnosis the problem.
Try adjusting the cable for the shift interlock, I will attach the procedure. This sounds like the problem you are having unless there is a mechanical problem in the transmission? In order to check that just remove the shift cable from the transmission and see if you can manually shift the transmission into gear and then see if it starts.
Try these and if you still need help just reply, if not click ACCEPT when we are done.
Correct cable adjustment is important to proper interlock operation. The gearshift cable must be correctly adjusted in order to shift out of PARK.