Well, if you have 60-18 volts on the track at the locomotive and the coupler doesn't fire, then it's probably going to have some kind of service. You might see if you can manually open the coupler. Take a paperclip and straighten it. Poke it in the coupler coil to release the coupler, see if it releases easily and closes without binding. It may be a bad coupler, but it might also be wiring. I wouldn't do many more coupler tries, if it's pinched wiring, you may cook the board, that will take longer to fix.