I'm afraid I'm have no idea how the Kenwood stuff works. Your best bet, unless someone else here can help, is to contact Kenwood or maybe Product Support
I have verified that the GPS DNX890HD is compatible with Express and the map update would be done with the Express program. This being said if you are still having issues there is a special support number for Kenwood devices. Contact 855-607-2536 for Garmin Kenwood support.