For GDB v2.0, there is round button on the GDB box. Hold the button for 15 seconds. You will see the LED light blink red every two seconds. Tap ‘+’ in ‘My Devices’ view in the GDB remote app to setup the device again.
For GDB v1.0, there is a button on the garagedoorbuddy box next to the power connector and ethernet connector port. To reset the password to factory default, hold the button down for 10 seconds.