There are a couple of possible reasons for this. The most obvious is that the Pulse is connected to someone else’s phone. First step, check to see if anyone around you has the Pulse app running and has connected to your Pulse.
Next step is to push the measurement button on the Pulse. This will tell you the battery is fine because you will see the measurement lights flash and second it will refresh the Bluetooth communications, so check the list again.
Last step is to turn off the Bluetooth on your phone the remove the battery from the Pulse for a few seconds. Put the battery back into the pulse, wait for it to boot up (the measurement lights will stop flashing) then turn the Bluetooth back on your phone. This will have fully reset the Pulse and you should see it on the “Select Device” list.