Itīs says wating-for-device when the fastboot client on the phone is not activated. Which leads me to belive you are not fastboot mode. When the phone is turned on as normal you can get there by typing "adb reboot bootloader". If you also have adb on your computer.
Or when turned off, hold power + volume down. This will enter the phone in bootloader state. Scroll with volume buttons to fastboot and press power to confirm. IF there is a usb connection when entering the bootloader the phone will automatically enter fastboot mode and the above navigation through the menu should not be needed.
There will be a red text declaring fastboot usb when you are set up.