This error indicates that DHCPv6 has timed out without receiving a response from the DHCPv6 server.
Things to try:
dhcpd: Solicit message from fe80::5054:ff:fe12:3456 port 546, transaction ID 0x25C85200 dhcpd: Sending Advertise to fe80::5054:ff:fe12:3456 port 546 dhcpd: Request message from fe80::5054:ff:fe12:3456 port 546, transaction ID 0x25C85200 dhcpd: Sending Reply to fe80::5054:ff:fe12:3456 port 546