I'm sorry to hear you're having trouble with the watch you purchased from another user. Do you recall if they had removed the watch from their account, including the NumberShare connection, prior to selling to to you? As smartwatches include a pre-installed eSIM, which means it is downloaded to the device as part of the activation process. This is not something that can be changed, so if it was tied to the previous user, it would refuse to activate elsewhere. Since this watch was purchased through a private transaction between you and this other person, we would be very limited on any sort of replacement options on the watch, so I would recommend either going back to the store you visited with this seller if possible, or return the watch to them and get your money back since it won't work for your account at this time.