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I just bought an Apple Watch Series 3. I have an iPhone 6 Plus updated to the version 12.4.3. I successfully went through the entire process up until the very last step on the Apple Watch. It had a black screen with dashes formed in a circle that were slowly going from Gray to White. I assumed this meant the process was almost finalized then all of a sudden my iPhone watch app Said it was unpairing the Devices though I had not even touched either device. I have restarted both devices. I have made sure to disconnect my iPhone from the watch in my settings and also in the watch app then restarted both devices once again. Airplane mode is turned off, and both Wi-Fi and Bluetooth are turned on. I have no issues getting the devices to pair up however it continues to say I need to update my iPhone though I already have. I have been just dying to finally get an Apple Watch and would really appreciate some insight.
Did you buy the watch new or used? I know from experience that if the display has been replaced previously with one that does not have the right antenna attached (GPS only or GPS+LTE), it can cause issues when trying to pair with a new device. You may need to return this watch and/or exchange it for another one to finish the set-up process.
You need to use the iPhones camera to look at the watch face with the pattern! This is how the phone and the watch validate each other. Start again following these steps Set up your Apple Watch aim your iPhone onto the watches screen as expressed in Step3 Update (11/22/2019) @kaelynnrenae - No I did read your description and was (and still am confused) as you have two stories here. One is the upgrade process and the second is the hand-shake of a fresh install to your iPhone. As this point I think you’ll need to wipe the watch clean and start afresh. If the watch is frozen presently follow this guide Fix a Frozen or Malfunctioning Apple Watch by Restarting It The only thing I can see here is About Activation Lock on your Apple Watch but what got me on this is the watch was cleared by the previous owner otherwise you couldn’t have tied it to your iPhone (Apple ID) when you bought it (unless you never linked it). So if the original owner enabled Activation Lock then the watch needs to be cleared by the original owner to allow you to use it.
