I just wanted to post and say that I've lost the ability to enable IPv6 on my leased Pace 5268AC yesterday when my account was upgraded from VDSL Fusion x1 to x2. Prior I had enabled and working IPv6 on x1 with the 5268AC. I'm not sure if the x1->x2 was the cause, but now when I log into membertools this is what I see:
I called in and talked to a very nice rep (Britney I think) who had me try a few things (factory reset, resyncing the modem from her side, checked the firmware revision) and also talked to a supervisor and the network team. They said that IPv6 isn't officially supported. It was my impression that IPv6 for xDSL Fusion using a leased modem is in fact supported, but I didn't argue since I'm not sure. Having said that, they're going to swap out my modem, which I hope fixes the issue. Anything else I can try?