That's a particularly German situation then I think if you mean it's IPv6 only. How do they support the many devices that don't yet support IPv6? Or if you mean that IPv6 AND IPv4 are enabled by...

Do you live in a block of flats or similar? It would be unusual for Powerline signals to travel between building as powerline signals don't tend to be strong enough to cross the mains utility cables...

Have you downloaded the latest utility version from the support website? Installed the latest firmware?

Try a hard reset? Or If there is newer firmware then use the recovery utility I posted elsewhere on here and update it.

I'm not aware of a single ISP that defaults solely to "hooking you up" to IPv6. Sure many of them support it but for niche uses and you usually have to choose to enable it or even request it be...

That does seem sucky that you have to ask, but then I guess these are sold as consumer level devices and relatively few home users need IPv6 these days!