727 trans stays in neutral. Help.

I have a 67 New Yorker that I added the Transgo 2 reprogramming kit to. The car drove for 2-3 miles then it stopped. It acts like it's in neutral regardless of which gear it's in. The shifter moves the gear selector at the transmission but the car won't move. I've checked trans fluid and it's full with the car running. Can anyone offer any advice??