Pairing apple watch.

hi everyone!

I just found an apple watch series 3 and it just like new because no one used it for 3 year since my father bought it! I’m trying to pairing it with my iphone 12 promax and updated to the newest version which is 15.6 but it still stuck on the software update screen. I tried a lot of things to fix it: factories reset the watch, restart both of my devices, uninstall watch app and reinstall it again. And now it still stuck on the software update screen.

Can anyone help me please!!!

Thank you so much!