I GOT IT TO WORK --- Not really sure which step did the trick. But here's what I did. I had an Apple Watch 4 Series, connecting to iPhone 12 Max Pro with latest iOS (16.2). Nothing was working. Would pair, and then say "unable to update". Initially when I would try to manually pair it wouldn't work. No pin would show up. Finally, what I did was, I switched to 2.5GHZ wifi network (if you have 5G you can call your ISP and have them split your network into 2) and then I restarted the watch. Finally, I tried to do it manually after restarting over 20+ times. And boom... Miraculously worked.