Best I remember there is a small plate with two bolts that keeps the parking pawl in place. Don't think it can be installed wrong, but maybe not there at all.

My first thought is that the linkage is not being moved enough to push the parking rod into place.

Disconnect the linkage on the outside of the transmission and see if you can move the transmission into park, and compare the position of the outside link with when the rest of the linkage is installed.