Chromebook OS error

Insert Acer C720 recovery flash drive in to the Chromebook.
Press ESC+Refresh(F3) and then turn on the power
When OS Recovery competes, remove flash drive to reboot computer
At the Chromebook "Welcome" screen, press CTRL-ALT-Forward(F2) to enter Terminal Mode
Login as user "chronos" (no password)
Obtain super-user access by entering the command: "sudo su"
Reset the GBB Flags by entering the following command: "/usr/share/vboot/bin/set_gbb_flags.sh 0x0"
Shutdown the chromebook by entering the following command: "shutdown -h now"
Turn on chromebook and enroll like a new device.