You may be gripping the heart rate handlebars too tightly, try to maintain a moderate pressure while holding onto the heart rate handlebars.
Try gripping the heart rate handlebars over the top, with your thumb next to your index finger instead of gripping it with your thumb under the handlebars.
Contact heart rate grips are not intended for continuous readings, instead, try holding the grips for 10-20 seconds at a time for an accurate reading.
Static electricity can damage the heart rate receiver and/or grips and can cause either a “HR” or no reading at all.
Remove the console and verify that the heart rate cables are attached properly, making sure that the cables are securely inserted into the console.