• The only thing I've found on this is:

    WAN_DHCP6 Stuck Pending / Unknown

    and its related (rejected) bug report:

    https://redmine.pfsense.org/issues/10565

    It's an old thread in the 2.5 Development Snapshots. But, I'm on the currently released 2.4.5-RELEASE-p1 (amd64) and have been seeing this same problem for months.

    Unlike that thread, I'm on Cox instead of Telus.

    It's not a very useful description of the problem, but in a nutshell, after some period of time the WAN_DHCP6 status in the Gateways section of the Dashboard will say:

    "WAN_DHCP6 Pending Pending Pending Unknown
    ~"

    The only way I've found to clear it is to either reboot the SG-4860 or go to Interfaces > WAN > SAVE > Apply Changes.

    The WAN_DHCP6 entry will then revert to something normal, but will, at some point, fail back to that Pending/Unknown state.

    This is how the WAN interface is configured:

    IPv4 Configuration Type:  DHCP
    IPv6 Configuration Type:  DHCP6
    DHCPv6 Prefix Delegation size:  56
    Send IPv6 prefix hint
    Block private networks and loopback addresses
    Block bogon networks
    

    From the previous thread, I'm unsure if the problem is supposed to be resolved. So, I thought I'd report it here.