08-17-2016 22:39
08-17-2016 22:39
08-18-2016 05:53
08-18-2016 05:53
A warm welcome to the Community @Monb. Thanks for troubleshooting this inconvenience by yourself. I would like to know if your Flex is already paired? If it isn't, I recommend restarting your tracker by following @SunsetRunner's instructions and after this process do the setup procedure one more time from your iOS Fitbit app.
I hope this helps, let me know the outcome.