Can't connect/pair new apple watch series 2 to my Iphone 6
So I brought a brand new apple watch series 2 of ebay but it won't pair with my iphone 6. It just comes up with "Iphone is out of date". But when I go to update my phone 6 my phone is up to date. What is annoying is that I have looked about and there should be no hardware or software problems with the series 2. As another note would it be worth sending the person who I brought the watch of to make sure it is not connected to their apple ID still?