Xfinity Home Customer Cannot Access VPN to Comcast Business Customer

Due to COVID-19, trying to setup customer to access their corporate network via VPN from home.  This person is an Xfinity home customer.  The business is a Comcast Business customer with static IP.

While at home, cannot access via VPN, HTTPS or ping/ICMP the IP address of the VPN device at their office which is a Comcast Business static IP.  However, if the laptop is connected through an iPhone hotspot, there are no issues whatsoever.  Any other user connecting over different ISP (i.e., AT&T) works fine.

The firewall on the cable modem for Xfinity home has absolutely nothing blocked - any other website such as google, Amazon, etc. work fine.  E-mail to Office 365 works fine.  It is just this connection to the Comcast business IP that's an issue...that's why I'm posting here instead of contacting Xfinity home support.  I've done I.T. work for 25+ yrs. now (not that I'm incapable of making mistakes, including obvious ones) but this looks exactly like Comcast is blocking access either from Xfinity home sources to Comcast business...doesn't make sense, I know, but posting here to see if anyone else has experienced?  Any help or suggestions are appreciated!