Wise words. Not replying to the OP so hopefully he reads down a bit. It looks like his drivers are not working, i.e. the fastboot ones since he can adb. If he's on Windows then device manager should show an exclamation mark or unknown device. There is a fastboot installation, let me take a look see if I can find it. Ok here ya go.
https://www.androidusbdrivers.com/google-pixel-usb-drivers/ I actually didn't need to do that exact procedure but I've been fastbooting for some time.
To the OP. You need to get 'fastboot devices' command to show your device when connected via usb to your computer and in bootloader mode. Once it sees the device the rest is child's play.
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See above.