Computer doesn't recognize Nexus7 on bootloader mode

[AC Question]

Hi I'm trying to install Android L on my N7 (2013). I found this video: https://www.youtube.com/watch?v=jdIvLK5jyHw and followed it step by step. My problem is that, when doing the 'flash all' step, the N7 needs to be on bootloader mode and connected to the computer.. So, I click on 'flash all', and the only thing I see on the screen is 'waiting for device'. I go to the computer folder and there's no track of the N7. I go to the 'devices and printers' folder on the computer, and there's a non specified Android device. I click on the 'solve problem' option, and it says that the N7 doesn't have a controller and it doesn't give any solution. So, the computer doesn't recognize the device, so I can't flash it. The curious thing is that if I start the N7 normally, the computer recognizes it. Thanks in advance.

 

[RumoredNow]

You do know that the Images for L are Beta Testing images and not made for daily use???

Are you sure you are qualified as a Beta tester? If you can't get your device recognized by your PC in bootloader mode, I'm not sure you are ready for Developer Previewing...

Why are you following some dude's YouTube vid and not the official install Wiki?
Setting Up the Preview SDK | Android Developers

Here's hoping you don't Bork too much.