I did this and my number sync keep turning off. I've spent 2 weeks and countless visits and I'm ready to throw the watch away. This isnt worth the time I've spent to resolve this!! So frustrated.
I have had same issues and also tried the new account which did not work.
I have Gear S3 LTE and S10+, unpaired bluetooth and it started working again, I just do not use BT with it any longer, with AT&T Unlimited plan it does not make a difference.
Thank you so much for sharing. I changed my Samsung account ID and the numbersync worked. This post should be at the top for everyone that is having this problem to see. I originally was using my AT&T account ID and I believe that is what most people have been doing thus causing the numbersync issue. My esim number is linked to a different email address than the one I use for my phone service and now numbersync works.
1. Unpair the watch (bluetooth) on your phone
2. Pair the watch (bluetooth) on your phone which will initiate setup
3. Go to watch settings, Connections, AT&T Number Sync and turn back on.
4. Wait a few minutes and it will connect