I have an iPhone 11 with the 14.6 iOS and could not pair my series 3 watch because the phone said it could not connect to the internet. Called Apple and the tech did a lot of troubleshooting and finally said the watch was bad and had to be sent in for repair.
FIX!- I was able to pair it on another iPhone 8 that had iOS 14.6 AND complete the download. I then unpaired it from the iPhone 8 and paired it to my iPhone 11. No issues. Find a friend with an older model iPhone or use one of your older model phone seems to be a work around.