Last week, my One seemed to only record my steps in the house, maybe in range of my Wifi. Even the time was wrong because it kept turning on and off. Then when I ran it didn't record any of those steps. Starting this week, it's working fine again with no explanation. It already showed the 6.64 firmware version last week so that's not it. I had tried plugging it in, turning it off and back on again as suggested by Fitbit. Nothing worked. Now it's fine. No idea. I had unplugged the dongle because I got a new computer and with the Windows Store Fitbit app update it seemed to work fine without it. The only thing I didd was plug it back in again for one update of my exercise then unplugged the dongle and now it works.
