I've had this happen to me a couple of times...
Now, apologies if you know how this all works, but...
The recording/tracking of overnight estimated oxygen saturation (SpO2) is driven by an app within the Fitbit app itself. This app a) has to be installed and (this is an important piece of info) b) has to be kept up to date by you (the user) - if the app software within the app is updated by the fitbit devs, there isn't an automatic update process for the fitbit app to install the update. One only knows that there is an issue where an update is needed if the tracking of SpO2 all of a sudden stops.
So to check if the app is installed, or needs an update:
1) on the fitbit app, go to your account (the 'button' at the top left of the app
2) in your account, select your device
3) select Gallery
4) select Apps
5) find and select SpO2
This will show you the status..
If the app isn't installed, you'll be able to install it and it will track SpO2 from your next sleep
If it is installed and there is an update available, you'll get the update option, so update it and it should start tracking again as from tonight
If, however, your app shows you a - Uninstall, then you've got the app set up and it's up to date (for me, it shows an app last updated date of 1 April 2021, and a version # of 1.100.43). This is where my knowledge of this comes to an end 😄 - the times where my SpO2 has stopped tracking has been where the underlying app on the app has updated
Hope this makes sense and gets you going again...but if everything is already 'in order', then we'll need to seek a bit more assistance!
