This article is from the VW Technical FAQ, by with numerous contributions by Jan Vandenbrande others.
A: The code has to be activated before it will lock up the radio.
This is normally done right after you buy the car, but nowadays
with the sad dealer service it is often overlooked.
See the "coding radio" archive on how to do this, but it basically
comes down to entering the code as though the radio had locked up.
 
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