We finally got this working - it turns out we were not using the primary account, instead we were using an account manager account which failed every time even with multiple reset and reboot of both devices. After we reset phone and removed all caching for the account and utilized the primary account setup was successful. What I had noticed was that if you login to the Xfinity mobile site on a computer and click devices, add a device and validated the IMEI for the watch it said compatible but then failed to add the watch as it said I was not the primary account holder with the credentials I was logged in which made me aware of this issue. In the end we didn't need to actually add the watch via this step in the web-browser on the computer, but once we had the primary account holder login and were using that as part of the setup on the phone with the watch we were able to successfully get through all the setup steps.
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I am also having these same issues trying to get an Applewatch activated and also tried adding as an extra line from the xfinity mobile account page, but then xfinity mobile webpage telling me I am not the primary account holder on the account? How do we tell who is the primary account holder? My mom's login fails with this message immediately after trying to login to the mobile site and I get logged in but when I try to add the BYOB line it then fails into this process telling me I am not the primary account holder and says "primary account holder for your Xfinity Internet account may create an Xfinity Mobile account".
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