Truck has a set of contactors for each drive motor. For them both to be powered, the steered tire must be within 30 degrees of straight. I would check or replace the floorplate or deadman switch first. I have seen some resistance in this switch allow the power steering to come on, but not the travel. The next switch to check is the one under the brake pedal. The third and fourth switches would be the forward and reverse switches. These operate off a cam when you move the control handle. I would also check the two 140 amp fuses on the contactor panel. One is for the left drive motor, and one is for the right. If you have the steered wheel turned to the left of right, and one drive fuse is open, you might not get the contactors to pull in. The motor controller will sense an open circuit and not allow travel. I would also check to see if you have any contactors welded or stuck. The 1A, or high speed contactor being welded will prevent travel. Pull all the plugs from the EV100 control card and make sure all the female pins are fully inserted. They must be in order to contact the male pins in the control card and allow travel. There are two switches on the steer wheel assembly that open as you turn left or right that you can check. The last resort is to call a lift truck repair company. Most will have a handset you can plug into this to do some diagnostics. If they send someone out, make sure to tell them they need to bring a EV100 LX hand set. Many brands of lift trucks used this GE motor contoller such as Clark, Mitsubishi, Komatsu, Hyster, Yale, Caterpillar.