I've just bought a Galaxy Active 2 and had no difficulty pairing it with my S10. The watch records all the usual data relating to steps, HR, sleep etc and feeds that through to the Samsung Health app on my phone.
Within the app, there are options to manually take a HR and stress reading. However, when I try to use these the app tries to detect the data from a sensor on the back of the phone, which the S10 does not have, rather than from the watch. It is registered as an accessory in the app.
I've spent far too much time searching for solutions on the watch, the phone and community forums but can't work out what I have missed doing, if anything at all.
Can anyone put me out of my misery (so to speak)?
That feature was removed from the phone, S21 does not have it. It might be the last Samsung Health update removed that. It seems it was transferred to the watch.