Is the check engine light on? If it is, do you know the code?
I attached a flow chart and possible issues.
The throttle position sensor is critical in shifting. If the ECM does not see the signal, it will not shift.
Check the voltage with a scan tool to see if there is a signal being sent to the ECM.
Images (Click to enlarge)
Thursday, February 13th, 2020 AT 6:59 PM