In order to Reset the Fibaro FGMS-001 ZW5 Motion Sensor, follow the below procedure:
Twist and remove the back cover of the Fibaro FGMS-001 ZW5 Motion Sensor.
Press and hold the B-button for 4 - 6 seconds until the LED glows Yellow.
Release the B-button.
Click the B-button once and the LED glows red and then fades, acknowledging that the sensor is reset.