Echo needs to be in the foreground of your phone to establish a connection. Once connected, it can run in the background. 

How to connect

1. Open Echo on your phone (you do not need to do anything on your watch). Tap to start so it says, 'Waiting to connect'
   
2. Press the left side button on the ELEMNT to access the settings menu
   
3. Use the down button on the right side of the ELEMNT to scroll to 'Add Sensor'
   
4. Bring Echo and ELEMNT near each other, then press 'Save Heartrate'
   

Additional info can be found on Wahoo's support page

If BPM field is missing from the ELEMNT dashboard but Echo is paired as a sensor, you must 'forget' the sensor and re-add it in order to add the BPM field.