pfSense

1) The DHCPv6 Server & RA page is not allow to enter IPv6 address in DDNS Server IP field (IPv4?)
2) The DHCPv6 Server & RA page DDNS Domain Key name may only contain the characters a-z, A-Z 0-9, '-' and '_'
'=', '@', '.', '^', etc. are special characters and dhcpd doesn't start if config contains it
3) The DynDNS secret must be enclosed in quotes (“secret”), otherwise you will get error message:

/services_dhcpv6.php: The command '/usr/local/sbin/dhcpd -6 -user dhcpd -group _dhcp -chroot /var/dhcpd -cf /etc/dhcpdv6.conf -pf /var/run/dhcpdv6.pid vtnet2' returned exit code '1', the output was 'Internet Systems Consortium DHCP Server 4.4.1 Copyright 2004-2018 Internet Systems Consortium. All rights reserved. For info, please visit https://www.isc.org/software/dhcp/ /etc/dhcpdv6.conf line 27: partial base64 value left over: 3. \x09secret 123; ^ Configuration file errors encountered -- exiting If you think you have received this message due to a bug rather than a configuration issue please read the section on submitting bugs on either our web page at www.isc.org or in the README file before submitting a bug. These pages explain the proper process and the information we find helpful for debugging. exiting.'

tested on pfSense 2.5.0.a.20200314.1917