Not sue if this helps but:
Unlike most Bluetooth accessories, your Flex must be paired directly through the
Fitbit App, and not through your Android device?s Bluetooth preferences.
1. Open the Fitbit App.
2. Account Setup:
a. Select Get started if you don?t already have a Fitbit.com account.
b. Select Log in to log into your existing Fitbit.com account.
3. Enter the email address and password for your Fitbit account and tap Sign Up.
4. Enter your personal details, then tap Save. This information personalizes your
Fitbit experience and improves the accuracy of your calorie burn and distance
data. This personal information is, by default, only visible to your friends, but
you can adjust your privacy settings on the Fitbit website to control what
information is shared with others.
5. Tap Set up Now.
6. Choose Flex and follow the onscreen prompts.
7. Tap I?m Ready to begin searching for your Flex.
8. Once found, the lights on your Flex will begin to blink. Tap the window of your
Flex repeatedly with your finger until it vibrates. If you have trouble finding
your Flex, tap Try Again and follow the onscreen instructions for help.
9. Once the Fitbit App shows the message ?You?re all set!? you can tap Go To
Dashboard to complete setup.