My name is***** will try my best to help you with your question.
1. First, make sure you have the correct time zone / daylight savings time setting enabled. Sometimes an incorrectly set time can cause pairing problems.
2. Try pairing the Vivofit2 with a different phone to help determine if the problem is with the Garmin device or just with your phone.
3. The easiest to pair the HRM is if you are paired with a smartphone, then using Garmin Connect Mobile, you can access the device settings and simply turn on the HEART RATE screen.
Once you make these changes, you will need to SYNC the Vivofit2 so that the changes can be applied to the device. Now, simply press the button on your Vivofit2 to switch to the HEART screen. It should pair and display your heart rate when you are wearing the strap.
--------------------Kindly rate my service 5 stars at the top of your question page if my answer helped so I am rewarded for my time; tips appreciated :)You can always reply back at any time if you need further assistance.Pete.--------------------