When you tell the engine to go forward, does it go backwards, by any chance?
One possibility is that you got the plug in the wrong way. The people that designed these did so in a way that you wouldn't destroy anything if you got it backwards, but there would be problems. Depending on the decoder and engine, you may find that the engine runs backwards, or the lights don't work. Try reversing the orientation of the plug and see if that fixes it.
It takes an iron man to play with a toy iron horse.
- Luke
Modeling the Southern Pacific in the 1960's-1980's