I just figure it out, WD’s documentation is very confusing.
If the box still blink after 1 minute, the reset has failed, you need to do it agin.
- press rest button with pin for 60 seconds, but the LED will NOT blink, however, stop pressing the button
- After 5-10 seconds the mycloud will turn off by itself and start reboot
- After reboot, LED will start blinking for 2-3 minutes, then it will reboot again
- Voila, now mycloud is factory reset