Polar coded heart rate pick-ups. 

The culprit for inconsistent heart rate pick-up is usually the heart rate strap: 

• Either the battery is dead or the wiring in the strap has been damaged.  Both the battery and the strap can be easily replaced.  https://korr.com/product/coded-heart-rate-chest-strap/
• At times, the black heart rate pick-up box can become damaged at the jack connector, causing an intermittent signal.  New pick-ups can be purchased on korr.com.  
• Lastly, the heart rate jack mechanism within the unit can become damaged, requiring repair at a KORR certified service center.

Blue tooth heart rate monitors.  

• Battery level of the heart rate monitor can be checked in the “About” section of the hardware. 
• Ensure that you are connected to the correct heart rate monitor.  
• If the Bluetooth seems to be the issue, make sure the airplane mode is off and Bluetooth is running on your computer.  If necessary, restart the computer and the CardioCoach software.