If you could just clarify if you're trying to get LAN IPv6 addresses allocated or something else.
$ ping6 google.comconnect: Network is unreachable
$ ping6 google.comping6: UDP connect: No route to host
$ ping6 google.comPING6(56=40+8+8 bytes) 2001:985:509c:1:20e:c4ff:DEAD:DEAD --> 2a00:1450:4002:808::200e16 bytes from 2a00:1450:4002:808::200e, icmp_seq=0 hlim=53 time=20.743 ms
Do you have the router advertisements service enabled on the LAN interface?