Transmission and speedometer quick working on 1996 Chevrolet Lumina

After I changed the serpentine belt, the transmission doesn't shift and the speedometer doesn't work. What could I have touched or undone?

Asked by for the 1996 Chevrolet Lumina
vehicle speed sensor is below the engine on the same side. did the belt break and fly around??

No, I needed a new serpentine belt for inspection and my husband changed it for me and then the transmission won't shift and the speedometer doesn't work.
there is a sensor below the area where the belt is located on the passenger side. if that is disconnected, then it will cause problems. have him use a flashlight and look around. it is a 2 wire sensor.