Welcome to the forum!
What is the number on the side of the locomotive?

It sounds like the e-unit may either be locked in neutral, or is not functioning properly. Do you hear a buzz from inside the locomotive? If not, move the silver lever on top of the locomotive to the opposite direction and cycle the power on and off with the transformer. The locomotive should run. If not, remove the boiler from the locomotive, and watch the e-unit plunger as you cycle the power on and off with the transformer. It should turn the plastic drum a bit every time it cycles. If this does not happen, you may have an issue with the e-unit, or the power wiring to it.

As a matter of standard maintenance, clean all old oil and grease from the motor, wheels, and roller pickups with hardware store naphtha. Lightly oil the axle bearings, both ends of the motor armature shaft, and lightly grease the gears.

You may alternatively have a motor issue causing your problem, but it must be determined first if the e-unit is functioning properly or not, before we move on to the next step in the diagnosis and repair.

Larry