If I am remembering correctly there are several things that have to happen before the computer will allow an OD signal to be sent. Engine up to temp is one. Temp sensor and wiring ok? TPS in correct range. Speed sensor in range.

Does it feel like the torque convert is locking up at the right time? If the TC is not locking/unlocking (given that you have a lock up trans) there might be bigger issues.

Or the button is pushed to keep the OD off as was suggested earlier.