You will have to do the diagnostics, so here's what I do when presented with a DCC fitted loco that 'doesn't respond'. I'll assume in what
follows that you done the basics of ensuring that DCC track power is reaching the decoder terminals, if not, loco body off and start there!
If on taking the body off there's a nasty pong of crisped electronic components, then you know where you are at. No resolution? Then:
Put it on programme track and attempt to read the address. If that proves possible and you have the expected address, try on DCC
power. If it works normally you are all done. (Seen this several times over the years.)
If not, try a decoder reset. (May need more than one go to get to address 03.) Alter address to what you want (and alter any other
settings to taste) and test on DCC power. (That usually fixes it, I have 'recovered' any number of apparently failed decoders this way.)
Still no go? Remove decoder, install blanking plate, test on DC (use a 9V PP9 battery if you don't have a DC controller) to see if the loco
runs when the motor gets power. If it does, install a different decoder, test install on programme track, and see if it runs on DCC (It will.)
If it won't run on DC, then check the circuit from the socket to the motor, and the motor alone.
Don't chuck the decoder just yet. If there is no visible evidence of damage to the decoder, try a few more resets. I have several decoders
still working as well as ever they did, needing several reset attempts, until one 'took'. (Great advice from a German retailer early in my
DCC experience - he said it made him very popular with his customers!)
Good luck.