Fitbit Product Experts Alumni are retired members of the Fitbit Product Expert Program. Learn more
Welcome to the Fitbit community, @Tuan.nguyenanh!
Sad to hear that you're having issues with your Charge 6.
To hopefully get SpO2 tracking fixed, please have a closer look at 'Why didn’t I receive SpO2 data?' following this link:
How do I track blood oxygen saturation (SpO2) with my Fitbit device?
For troubleshooting your Strava syncing issues please check this: