Did you use another Fitbit in Wokamon before getting the Blaze? You might want to try to revoke Fitbit authorization to Wokamon first.
To revoke authorization:
1. Go to www.fitbit.com and log in
2. Go to Account settings (top right icon on dashboard page) > Applications
3. Find 'Wokamon by Noodum' and revoke access
Reconnect Fitbit after revoking access in Wokamon:
1. Please make sure Wokamon is removed from background before re-entering the game
2. Go to 'ME' > 'SYNC OPTIONS' > tap FITBIT to initiate the authorization process
4. Please make sure you tick the 'activity and exercise' box when the Fitbit authorization window pops up
5. Tap allow button and follow the prompt to go back to the game
Please let me know how you go with this.