transmission problem on 1996 Plymouth Breeze

I have just replaced the transmission but this transmission doesn't change gears when moving. However, when the car is not moving I can manually place the transmission in each gear level: 1st; 2nd; 3rd and reverse and the car will drive. Can you make a suggestion as to what the problem is?

3 answers
There is a problem with the replaced trans, it is not working properly. Take it back to who ever did the work.
speed sensor(s)
my car wouldnt shift out of low gear and it was stalling after it reached certain temp.My mechanic replaced the crank case sensor and the tranny started shifting again.