We apologize for the inconvenience! We hate an error message. If you're seeing Fitbit- no tracker paired 904 error, this message means the Fitbit account you're trying to sync to your Sonic Boom account doesn't have a Fitbit device registered to it.
To remedy, double check you're using the correct Fitbit account credentials when syncing your accounts. Follow these steps:
Open the Fitbit app.
In the upper right corner, click on the "ID card" icon to open your account settings.
Scroll down and click on "Security and Login" to find the email address associated with the account. Does it match the one being used to link Fitbit to Sonic Boom? They should match!
Of course, make sure you've actually synced your Fitbit device upon setting up your Fitbit account!