Can't Login with Comcast Business credentials on xfinitywifi Public Wi-Fi Captive Portal

I have found that, over the past 2 years, when accessing a public "xfinitywifi" SSID hotspot from ANY LOCATION in the Memphis, TN metro area (can't confirm outside of this area?), from ANY DEVICE (Windows, Mac, iOS, Android have all been tested), the captive portal assistant on whatever device will popup with the page about purchasing a pass. If you click the link at the top for current Xfinity customers to sign in it takes you to an Xfinity login screen. Up until this point, pages load quickly without delay or issue. However, if you then click the link to sign in with a Comcast Business account specifically, the page never loads and will eventually time out.

A few years ago this worked beautifully and I would constantly log our iPads into xfinitiwifi hotspots when we were out at restaurants using my Comcast Business account. You could even then, after authenticating, download and load the .mobileconfig profile to connect to the upgraded Xfinity Mobile SSID. Then, sometime about 2 years ago, we started seeing this behavior where the captive portal sessions started blocking the Comcast Business pages from loading correctly. This has been an ongoing issue for years now. It's not even related to a specific device or account, since you can't even get that far to type a email address. 

I know for certain the issue exists all in my immediate metro-Memphis area, but can't say for certain the issue exists outside my market.

I'm a Wi-Fi and Network engineer myself, and this seems like a wireless captive portal ACL issue where the Comcast Business domain and/or URL isn't whitelisted in the captive portal profile thats being applied to wifi clients on the xfinitywifi SSID.

I have to imagine others have encounted or are encountering this issue? If you have Comcast Business and are reading this, can you please test logging into a public xfinitiwifi hotspot?  I can't be the only Comcast Business user who is occasionally wanting to utilize public wifi hotspots?