Mine did the exact same thing, I got a warranty claim, they asked me to send it back, and it's been over two weeks without any replacement even sent. I'd suggest just getting a chargeback and finding a competitor. Wish I'd done that.
All,
I was using the Light watch face, which it a Fitbit-developed face. I contacted support and they sent a replacement. If you're having a similar problem, contact them -- they can walk you through possible fixes and arrange for the replacement if you're eligible.
Best AnswerDon’t plug the Fitbit device into the charging cable. Press and hold the button for about 8 seconds until the screen turns off. After the screen turns off, you'll feel a short vibration: When you feel the vibration, release the button and immediately press and hold the button again. Wait until the blue logo appears, then disappears: Immediately release the button and then immediately press and hold it .again, until you feel a vibration. After you feel the vibration, release the button. This vibration indicates you started the factory reset. Wait for approximately 12 minutes while the device clears all data. Eventually, the Fitbit logo appears and the device boots and displays Fitbit.com/setup Wait for a couple of minutes. wait until the Fitbit logo comes back with different languages. You just have to setup it up on your phone again just like you did the first time you setup the Fitbit. On the setup page, you will see the "Replace". Tap that then proceed. During setup, it will ask you to update the firmware that will take a while. But after that, you are all set. I hope this helps.