My Apple Watch quit showing my activity on my current watch and is showing my old watch on top when I go into the setting for Activity. I have tried to move it down so that my new watch is on top but it doesn't move.

New series 8 Apple Watch does not show/allow me to add Blood Oxygen to Complications. It's in my dock and works well when I pull it up on apps in the list but I want to set it as a complications. Yesterday I lost Activity data and did a complete reboot/restore so now that works but I still am unable to get the Blood Oxygen added to the watch face. Thanks for any help.