Boy, we're lucky to have Klaus, the Wunderkind of TNCR if not the Western world. His 'wild guess' looks to be right on the money.
But look here: You can go to this site and it will presto like magic test your IPv6 connectivity. DO THIS if you want to prepare against being hurled without warning into the outer darkness like I was.
Carp, my dumb ass is showing again. If I list the addy for you to go to, I don't know if my IP number will show up in your box, or yours. I assume yours, because why would mine show to you? But the Internet is nefarious and evil. So Google 'Test your IPv6' and get to it that way, please.