Did you remove and reinstall the drive while in neutral gear? Ensure the jaws on the drive grabbed the shift cable end knob during installation.
Also did you set the new shift cable using the tools required to adjust the cable before installing the drive?
Sometimes due to the O-rings sliding into the gimbal bearing helps prevent you from pushing the drive all the way up to the bell housing completely/easily. If you have about half the threaded studs sticking out than you should be able to use the nuts to bring the drive up tight to the bell housing.
Excessive old grease build up inside the engine coupler could also affect easy installation.
Using the correct service manual?
Below are the tools needed to adjust the shift cable but some have used different methods to simulate using the tool such as a paint stirrer stick as the flat plate.