Not getting IPv6 Address

I get a DHCPv4 address, but no DHCPv6.

Xfinity support said the only thing they can do is send a new modem, but the new modem has the same problem. I want the modem to be in Bridge Mode, but it doesn't work in either mode.

 

This is what the gateway shows - you can see all the IPv6 values are missing - screeenshot also available here: https://i.imgur.com/Vzhuj9n.png

Screenshot of Modem Network Information

 

Anyone know what is going on? Is there any way to actual reach a network engineer at Xfinity who can do more than read from a script? (It seems like no one in customer service even knows what IPv6 is...)