I know some of us who bought apple watches or brought our own were having huge cellular activation problems ending with a Uh Oh screen.
After 3 weeks I went back into the Xfinity store after dealing with rep after rep over the phone who have no idea how to do their job or have people skills but the manager at the Xfinity store was fantastic. I live in MA and with me there were two problems. One on their end and the other may have been my mistake. For whatever reason there was something going on with zip codes in my area on their end (not sure how a zip code would cause problems) but here is what I was doing wrong. My fiance and I share a Xfinity mobile acct which is in her name. For whatever reason she could login using a iCloud.com email address so we figured that was the email and password we needed to use for activation. I got a call from a tier 3 rep and she had me login using my fiance Comcast.net email and password and it worked right away. So if you are using a different login other than your Comcast.net acct it wont recognize it for whatever reason. I also want to say thank you for the MOD ChrisL. He has kept in touch with me this entire time and keeping me as updated as he could. And other good news I am using public beta iOS 13 on my iphone XR and using watch iOS 6 public beta on my apple watch series 4 44mm so if you are having problems connecting thinking its because of the beta its not. Hope this helps some people and we all are able to start enjoying ALL our watch features that we pay for. feel free to PM me if needed.