Configuration of DynDNS settings to run with FreeDNS (afraid.org) and IPv6

Hello,

I would like to update my FreeDNS subdomain with an A-record and an AAAA-record. I have my Sophos UTM running behind a Fritz!Box, with the Sophos being an exposed host, both for IPv4 and IPv6. Thus, I need the Web service to generate the IPv4 adress as the public IPv4 adress sits on the Fritz!Box, but I need the IPv6 adress of my Sophos' WAN interface, as this is a subnet from the net I was assigned by my ISP.

Here is my DynDNS config, one for IPv4, one for IPv6.

And here my FreeDNS config:

Now the update process is stuck in: DynDNS IPv6 status is: An update attempt is in progress.

Could you advise, how I can get this running?

Thanks for your support!

Tim