For the last few years, I've been using the Sync Solver Fitbit to Health app with good results. It's a one-time purchase of $5. The same company also makes a Health to Fitbit version of the app ...
Fitbit was one of the pioneers of fitness tracking ... Alternatively, if it's lagging, not illuminating its screen, or failing to sync, you can restart the device without deleting all your data. Below ...