I just started using the web interface and I noticed that under Health Stats my body battery, stress and heart rate data do not come up at all (the sections are blank) but I see it on my watch. I see sleep and weight data just fine. I am using Safari on Mac OS if that makes a difference. I will try it also on my Windows PC to compare.
Edit: I logged into Garmin Connect web via Edge on PC and noticed that there my old tracker (vivosmart 4) was showing under devices but not my new one (245 music) What is interesting about that is that on Safari my 245 music was showing under devices. So not sure how/why they would be different depending on which browser or OS I used. Anyhow I updated it to show the 245 and now both the PC and my MAC show the missing stats on both.