Why will the car not go into overdrive. It is a 2004 corolla 4wd nze124 on 2004 Toyota Corolla

Driving on the highway, slowed down to a near stop cause of traffic, thereafter refused to go into over drive

Asked by for the 2004 Toyota Corolla
Is the overdrive off lamp "on" or "off"? Is the check engine light on? Has anyone pulled codes from the system? Common problems are with transmission fluid temperature sensor circuit, and with the OD switch circuit. These can both be monitored in scan data.
Over drive light will illuminate if pressed to the off position. The vehicle had a plugin service a day previously. The engine warning light is on as off this morning. 12hrs after the problem.
I solved the problem, the mechanic who did the computer plugin disconnected the overdrive switch, then did not reconnect properly.