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.

I can no longer track my exercises..or days of exercising. Only noticed a few weeks ago. Is this because of the changes? It is annoying@

My Fitbit stopped tracking my exercise. Annoying.  Did they need to screw with this?  If it ain't broke don't fix it. 🤬

I have this problem as well. I also do not get sleep data or readiness data. I bought the Charge 6 in July and am disappointed in the performance.

Half the time the spo oxygen levels don't show up either it says only 4 out of 5 when it's actually 5 out of 5 when you go into the stat chart very annoying if their going to update things via google now they could get it right otherwise go back to Fitbit running the show 😤