I've tried Wug's Nexus 7 toolkit but with no success. I get messages saying that fast boot cannot be found with a suggestion that I should try a different USB cable or a different USB port on my computer.
I have tried about 10 cables and tried all 4 of the USB ports on my computer but with no success.
I did root it eventually using Kingroot on the device, but now I want to un-root it so that I can upgrade to the latest Android release. I used Kingroot to do the job, and even though all the root testing programs say that it is unrooted, upgrades cannot be installed. Every time I attempt to do so I get an image of a dead Android and an message that says "Error". Does anyone have any suggestions on how to get my Nexus 7 back to it's original condition?