No coding on that device. What’s not happening Shack?
I was referring to the fact that as soon as I reconnected the battery, ignition key not in, before I got back in the car, the radio came straight on without a requirement for the radio code, or even to be switched on. 
It is an NCDC 2013. 
So aside from the radio, everything is working perfectly?
The NCDC2013 doesn't have a security code in the traditional sense - its security is by the fact its paired to the display in the dash. So you have no code to enter. So worry not about the fact its not asking for a code, as it won't

Most glitches with NCDC2013 can be resolved by popping the radio out for an hour - sometimes its internal systems get in a strange state, particularly as they age.
Check the Mode Retainment setting I suggested 2 or 3 posts ago as well.
Lastly, the radio (along with other stuff) works off the "W Contact":
Key just put in, but left in off - W off
Key in position 1 or II - W on
Key moved from I or II to Off BUT KEY not removed - W on
Key out - W off
So make sure W contact working as expected.