Why won’t my Apple Watch pair with my new iPhone?
Why won’t my Apple Watch pair with my iPhone 13
Apple Watch Series 3, watchOS 8
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Did you unpair it from your old iPhone? Or follow these steps:
How to pair your Apple Watch with a new iPhone - Apple Support
FWIW a lot of people have had trouble updating or pairing a series 3 watch. With the limited memory in a series 3 watch, your best option may be to make an appointment at the Genius Bar in an Apple Store near you and let them look at it:
Genius Bar Reservation and Apple Support Options - Apple
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