If you have changed your device, then any mapsource maps will no longer work.
They are keyed to the device ID of your original device.
I don't know how Garmin respond to requests for new unlock codes for device failures.
I'm going to guess it's a "Fuck Off And Buy The Maps Again". ( I may be wrong, but... )
I've long since given up on being compliant on this, and have gone to the dark side.
Google "gpsunderground", select garmin maps sub-forum, and start learning.
Be aware that garmin went through several stages of protection.
Which applies to you depends on the map version you have, and the device you use it on.
Original maps could be un-locked in mapsource using the Jetmouse 1.5 keygen.
You just input the mapset ID, your device ID, and it would generate an unlock-code which you could put into mapsource.
(Also note that Jetmouse 1.5 has a bug with certain map IDs, there is a patched version on gpsunderground.)
Later versions of mapsource went on-line to validate the keys, and so it bacame necesary to use patched versions of mapsource.
Later units use an additional protection method called GMA.
This requires further processing to remove from the .img files.
I really don't want to turn this into a warez forum, so I'm going to say no more on this matter.
gpsunderground is the place to learn more.