Mine also hasn't synced since Monday this week. SO frustrating! I'm going to call the help desk tomorrow.
Best AnswerI followed the advice on another thread - plugged my fitbit into the usb charger, held the button down for 15 seconds or so until it came back to the software version. Then when I unplugged it, it synced with the fitbit desktop on my computer. It still doesn't want to sync with the online dashboard, but at least it's working again.