Lezyne Heart Rate Flow Sensor
The first thing you'll want to do is update the sensor. Check out this article for more details.
To wake the heart rate monitor for pairing, put the sensor on. It will automatically display 65 bpm when it is paired to the device, but it has not yet detected a heartbeat. You may only need to wet the terminals under the strap to get it to start displaying a reading. If the displayed heart rate appears to have frozen on another number, remove the sensor from the strap, wait five seconds, and reattach it. It's also a good idea to store the sensor separate from the strap to preserve battery life.
Lezyne Cadence Speed Flow Sensor
The crank/pedal magnet passing over the sensor is what wakes the sensor. An LED will show through the plastic on the sensor for 30 seconds, and it will be available for pairing for 2 minutes.
We've seen very few problems with our speed/cadence sensors. More often than not, if you're experiencing an issue, it's magnet placement or the wheel circumference is incorrect. Please double check that the magnets are passing close enough to the sensor. We recommend 1-2 millimeters between the sensor arm and the spoke magnet; that's about a penny's width. The crank magnet needs to be within 5 millimeters.
If your bike is stored in a way that the magnet keeps waking the sensor in between rides, the battery could die prematurely.
Occasionally, the sensor arm can get turned or twisted too much and the wires running to it may have been damaged. You can check this by unscrewing the screw where the arm meets the body of the sensor and visually inspecting the wires.
If the bike hasn’t been ridden for a while or you’ve recently updated the device, you might see that you're not getting a reading. Navigate to Sensors in the GPS menu and make sure it is currently paired. Often it only takes a quick re-pairing of the sensor to the GPS to solve the issue.