I hope this helps. Which decoder in the loco? Bachmann decoders can be troublesome. SoundTraxx decoders and most others are ok.
https://ncedcc.zendesk.com/hc/en-us/articles/205053429-How-to-read-or-change-a-CVThere is a NCE Group in Yahoo Groups.
I use to use the Power Cab. I also cycle track power after a program change. Just to be sure. Can you read the decoder ID ok?
Rich