I've been using my Fitbit Sense2 since mid-June. Several apps within the app have not worked well, failing after I set them up. Notably, the ECG feature, which was my primary motivation for the purchase, has never worked, and the Alexa and calling features have failed.
on 10/22, my sleep data failed to show up, and I was subsequently unable to sync it to my Galaxy A13. Today, 10/23, I followed the directions on the website tech page, then called tech support and was guided for 30 minutes through even more steps via a very patient and kind representative identified as Valentina in Bogota, uninstalling and reinstalling, even doing a factory reset. The conclusion was that there is a problem with the Fitbit app, and the team is working on it...
The watch doesn't even show the correct time at present.