There are a couple of possible reasons for this.
- The first is that the Pulse is out of range/being blocked by something - bring the Pulse closer to the phone and take a measurement, this should bring it back into connection.
- The second option is that the battery has run out. If, when you take the measurement, you do not see any lights, or only see the low battery light, replace the battery.
If neither of these things help:
- Turn off Bluetooth on your phone
- Remove the battery from the Pulse meter for a few seconds
- Replace the battery and wait for the boot up sequence (flashing lights on the Pulse) to finish
- Turn the Bluetooth back on
The Pulse should now return to normal operation after connecting and synchronising.