Same issue as multiple users have posted. Since Oct 24 my Charge 2 will not sync to my app. It will on a day by day basis, which disappears the next day. I have the latest OS on both the Charge 2 and my phone. I have tried all of the troubleshooting posted for all of the same issue on the website.
Seems many, many, many users are having an issue- is a fix in the works?!?! I am considering switching to a different brand of tracker based on how this seems to be getting handled, which is unfortunate as I've used Fitbits for 15 years.