The Heart Rate Monitor doesn't work
The measurement may be impeded by a protective film on the sensor. Make sure there is no protective film on the sensor, and if there is, carefully remove it. Do not use sharp metal objects for this: as it may damage the sensor.
Keep the sensor clean at all times. Grease and dirt on its surface can significantly distort its operation and sensor readings.
Make sure that the device is tightly put on your hand. Heart rate monitor works correctly only when the sensor is close to the skin. To check your heart rate, go to the heart rate monitor section. Measure your pulse. The measured value must be displayed on the device screen.