I had problems unlocking the bootloader of my Nexus 5! The device was recognized and the folders were visible but was not detected when switched off. So I used "platform-tools" under Linux Mint (because under Windows 10 I have had problems) and, after having opened the folder of platform-tools as administrator, I typed the command lines, but with the smartphone turned on. It was successful unlocked. (Sorry for my English language which is not good)