Install Google USB Driver
Updated
For Pixel and other stock Android devices on Windows.
- Download the Google USB Driver from Android Developers.
- Put the device in Fastboot: power off, hold Power + Vol Down, plug in the USB cable.
- Open Device Manager → the device with a yellow mark (Android / ADB Interface) → Update Driver → Browse my computer → Let me pick → choose the driver folder.
- Done when it shows Android Bootloader Interface with no yellow mark.