Need help pairing new phone to Apple Watch
apple Watch won’t pair to new iPhone
iPhone 8, iOS 13
What series watch? What model iPhone? What iOS version is on it?
Identify your Apple Watch - Apple Support
Apple Watch Ultra, Apple Watch Series 8, and Apple Watch SE require an iPhone 8 or later with iOS 16 or later.
Apple Watch Ultra 2, Apple Watch Series 9, and Apple Watch SE require iPhone Xs or later with iOS 17 or later.