Got a second hand Polar Loop 2?
If you've purchased a second hand Polar Loop 2 and it fits your wrist as well, good for you. Hope you got a good deal. But you need to make sure the activity tracker is no longer tied to the user account of the previous owner. You can do that by resetting factory settings and registering the activity tracker to your own account. Otherwise all the activity and training data you collect will be synced to the Polar account of the previous owner.
Follow the related document link to the instructions on how to reset factory settings.