Error with Advanced Call Forwarding

We are trying to use the Advanced Call Forwarding with a long established Comcast/Xfinity account that includes two Xfinity Voice phone numbers.

We are logged into the account holder user (the only user on the account) and I can confirm in My Xfinity users that the user role is Primary.

However, under Xfinity Voice -> Settings -> Call Forwarding, the Advanced Call Forwarding and Selective Call Forwarding sections all remain greyed out.  Both text boxes and the Add buttons are greyed out.  Instead, there is a momentary message box with "An error occurred while processing your request.  Please log out of the application and try again. [404]"

According to the Chrome browser Inspect option, the URL generating the 404 is:

https://ott.comcast.net/xcportal/callfeatures/xcweb/1.0/[user name]/sns/[phone  number]

Logging out and then logging back in does not work.  It still continues to generate the same results.

Contacting customer service also does not help.  They indicated the issue had been escalated.  Someone left a voicemail the next day that they corrected the issue.  However, still getting the same exact results.  However, since contacting customer service, it s no longer possible to recieve in-bound calls via Xfinity Voice.  Outbound calls still work but calling in from *any* independent phone number just goes straight to voice mail.

Is anyone else able to access Advanced Call Forwarding?  Is this a known issue?  Is it typically for Comcast Support to take a voice line able to recieve phone calls and render it to going straight to voice mail to then claim it is now resolved?!   Is there any method to get the problem really resolved instead of Xfinity-grade broken level "resolved?"