Please list the product number. We can help you better with it. Sounds like a 3v system. Replace the battery with a BCR2, available from Model Train Stuff at about $20. Install the BCR2, then power up. It takes about 20-30 seconds for the locomotive to react and get the boards working. Next, try the sounds, whistle, uncoupler then move it. You must get it in neutral to do any feature/factory resets or recover. Try these first.
bruce