Single blinking blue light?

[IncognitoMode]

My new Flex 2 seems to track steps but erratically tracks sleep. I am trying to troubleshoot it and did notice that the only thing I can get from it is a single blue flashing light. 

The light turns off after a while and tapping the pebble makes it flash blue again. Notifications don't seem to work (trying to to do test notifications via the app). When charging, the four white pulsing lights do show. But returning it to the band, the blue light just flashes blue (blue light only no other white lights).

Any clues? I've tried restarting the pebble multiple times, reinstalled the app, and restarted my phone, and even "resynced/replaced" the pebble with my app/account.

[JohnnyRow]

My experience: don't try to get too smart about debugging it or outsmarting the sensor lights.  Does it track heart rate?  That's what it uses for tracking sleep.  That's all you need to know about sensors.

If it tracks sleep at all, even erratically, sensors are likely okay.  Perhaps tracker is moving around on wrist as you sleep.  Or try switching to other wrist at night.