I've tried all the solutions on here and they didn't work. Here's what I did that finally worked for me. My watch was unpaired to begin with so I can only speak on what helped me to pair it again.  Hard Reset BOTH iPhone and Apple Watch Remove Apple Watch from your iCloud (Settings --> Your Name/Apple ID) 3.Update your iPhone if it needs to be.  After Updating my iPhone and going through the pair steps, I no longer received the error message.  Hope this works for you! (iPhone 12 Plus iOS 14.4 ---> 14.8) Apple Watch Series 4 Updated to 7.6.2)