Why would I still have the same prob if I replaced ALL the Solenoids? on 2000 Ford Taurus

I have a 2000 Ford Taurus and it will not shift out of 1st gear. The light came on and said: Code PO750. Replaced all the solenoids and still the same problem and code came up. Replaced gear shift solenoid A. (All were replaced). Still same problem. Could it be wiring?

1 answer
Is the diagnosis being done with a 'code reader or a scan tool with live data to observe? Need to know what the TCM is commanding the solenoids to do. go from there.