Hello sjpt
I am ecstatic! Thank you soooo much! It worked!
The Kobo reader actually appeared on ADE and I followed your steps: Ctrl-shift-E
A box came up saying De-Authorize Device, which was weird because it would have meant that the device was already authorized ... although it did not work.
Nevertheless, I clicked on De-Authorize, closed down AED and then restarted it and, lo and behold, a box with the Device Set Up Assistant came up and all I needed to do was to click on Authorize.
To test it I dragged and dropped one book from my Library onto the Kobo Reader and it actually worked and is now on my Kobo Reader.
I still can't believe it - after spending countless hours trying and looking at helplines, etc I am up and running. What a relief. I can't thank you enough.
Kindest regards from a
Damsel-no-longer-in-Distress