Couple things to add
First I guess I'm glad I never got into Map Source and was then forced to change to BaseCamp, still just doing a little bit in BaseCamp, mostly bringing in the routes from events and getting them into my Zumo.
Second regarding connecting your Zumo to PC and having it recognized, not sure if it is something odd with my unit but sometimes it will go into powered mode, like I just plugged into a USB charger, then I need to disconnect and try again. (I have the same but opposite problem when trying to charge sometimes it thinks it is connected to a computer, my Garmin Nuvi2450 used to do this sometimes too.) Had this happen again yesterday when I connected to get my maps updated and load GPS routes for Mail Pouch.
PS Bob sorry to hear had your GPS come off, then had to watch as it was crushed by a car. I lost a GoPro off my helmet a couple years ago and was very bummed, I replaced it and have been extra careful since then, but also made sure to include name/address info on the memory cards.