Charge 3 resting heart rate no longer being recorded

[Banksie_FB5]

I have a Charge 3 and, until 6 days ago, was able to view all previously recorded resting HR data. Since then, no data has been recorded - I can see the live RHR but as for the averageRHR, my device still shows the rate last recorded 6 days ago and the dashboard on the app simply displays "- -" for the past 6 days.

How can I restore the ability to record the average RHR? I have re-synced the device with the app regularly and restarted the device twice (plug in to charger, hold button for 8 seconds, see smiley face etc.)

Thanks for any help / advice

Moderator edit: subject for clarity 

[LiliyaFitbit]

Welcome to the Fitbit Community, @Banksie_FB5.

Thanks for the details shared in your post and for already trying to resolve the issue. I recommend trying the following:

1. Log out from the Fitbit app.
2. Force quit the Fitbit app.
3. Reboot your phone.
4. Open the Fitbit app and log back into your account.
5. Review our tips in Why don't I see health metrics data? 

Hope this helps.