Fitbit One stopped syncing with app version 3.31

[JohnH.]

I updated the Fitbit app on my iPhone to version 3.31 last night.

Now it will not sync to my trusty Fitbit one.

I have logged off and on to the app.

Turned off my bluetooth and back on.

Reset my Fitbit One.

...   still not syncing...

Are there issues with version 3.31?

Moderator edit: subject for clarity 

[LiliyaFitbit]

Welcome to the Fitbit Community, @JohnH..

I am sorry to hear your Fitbit One stopped syncing after updating the Fitbit app to version 3.31. Thanks for trying to resolve this, I understand your concern and I am here to help. While you've tried some steps, please give a try to the following:

1. Remove your Fitbit and any other device from the Bluetooth settings on your phone.
2. Turn off other Bluetooth connections that are nearby.
3. Force quit the Fitbit app.
4. Reboot your phone and restart your Fitbit again with the steps from this help article.
5. Open the Fitbit app and pull down on the screen to force a manual sync and if a Pair authorization appears, tap pair.

For complete troubleshooting steps, see Why won't my Fitbit device sync?

Keep me posted on the outcome.