I was playing around with this today, mainly because I think the connected drive app is a bit clunky. When I hit the send to device option in google maps my car didn't show up, so I hit the help button and there is a link there to manually add your car.
If you follow the link below you can manually add your car, it links up to your connected drive username (no password required).
https://www.google.com.au/maps/sendt...ce=tldsi&hl=en
Once I added my car it then showed up in the send to device menu and it seemed to work.
Not sure if this will sort some of the issues people are having.