IPV6 no longer works after Service upgrade and new modem.

Hello,

Updated service (was blast and now extreme pro+) and modem, now IPV6 no longer wokrs. The new modem is an Arris T25. I see my router sending out a IPV6 RA and never see a response. I have not been able to get in touch with a person that understands my ask... any suggestions?

Thank You.