I have been running my Edge 840 with non-garmin maps lately and at the time Garmin Express also removed the basemaps from my device. Now however I want to return to using Garmin maps and I have reinstalled the maps I want through the latest(?) version of Garmin Express, but the basemaps no longer get installed together with the detailed maps. I have tried reinstalling several times but it was of no help sadly.
I'm also on the latest firmware release for my Garmin (and have been on the beta before) so I am using the new transfer protocol.