While all modern OS support the compressed IPv6 notation for DNS (2a0f:fc80::), some routers require you to enter the fully expanded notation (2a0f:fc80:0000:0000:0000:0000:0000:0000).

Help us fix this for everyone by asking your router manufacturer to support the compressed IPv6 notation for DNS.

Workaround

You can use this online tool to expand IPv6 addresses before entering them.