Bootloader unlocking veterans probably did the same thing I did when they first got their Nexus 6P. Of course the first thing I wanted to do was get that bootloader unlocked and get TWRP installed. I plugged my 6P into my PC and proceeded to boot the phone into fastboot mode so I could unlock the bootloader. After typing the normal command "fastboot oem unlock" and getting an error I scratched my head. In these situations google is indeed your friend. What I found within a few minutes of research is that the Nexus 6P requires a new command for unlocking the bootloader. The new command is as folows, "fastboot flashing unlock" Other commands include: fastboot flashing lock fastboot flashing unlock_critical fastboot flashing lock_critical fastboot flashing get_unlock_ability I am not sure why the change occurred, but this is generally the same easy process you just have to remember to include the "flashing"!