Apple watch update Error

I am trying to pair my apple watch that I got off of Amazon to my phone. There need to be an update because it is the series four. I bought it second handed. Every time I update, I get an error message that says my watch cant not update because of not internet connection. Which is false because I have tried four different WIFI connection spots and have spent hours waiting for this update to continue to set up my watch. I can not do that until the update is done. When I try to talk to apple support it does not go well because they need the serial number. I can not get the serial number because my watch has not been setup yet. Does anyone have any idea why my watch will not update so I can continue the setup process?