How do I unlock my new City Navigator North America NT DVD Maps?

Hi there I have a Garmin Street Pilot 2720 and I want to update the 2008 map set for a ride from BC Canada to Mexico so I purchased the CNNA NT DVD based on folks saying they could put some of the maps on their older 2720s.

I was able to unlock my new City Navigator North America NT DVD Maps using the Garmin http / my . garmin . com / maps / unlockmaps. htm , web site

But when I opened the MapSource software to transfer some of my new maps to my 2720 it said my new map set was still locked and when I clicked on the "Unlock Online" button it took me back to the same Garmin web site above, where I have already unlocked my new maps.

How do I unlock the map detail of my new maps in MapSource so I can put some of the maps on my Garmin Street Pilot 2720?

Thanks in advance.