Are you sure that you are using exact same unit name?
Not sure how but when I got for a first time at home my second hand unit somehow I managed to reset it's registration (it was registered already and I did not know previous details). Only what I can remeber was that I tried to reset it to factory defaults and at some point I managed to do it, but it was already registered with active registration. After firmware recovery there is no registration data at all, so probably you should on painful route - write to Netgear support to reset registration which is bound to your key.
