My Apple Watch SE won't pair with my iPhone
Will not pair with my iPhone 12?
[Re-Titled by Moderator]
iPhone 12, iOS 17
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Please see Apple's suggestions in If you can't pair an Apple Watch with your iPhone - Apple Support.
If that doesn't solve the problem please post back with more details and a description of what you see with your eyes when it fails (the error/failure message, etc will be very helpful).