How to correctly only update the public ipv6 prefix?

I have a HomeServer connected via LAN and a FritzBox 7530
I only got a own IPv6 Adress, my IPv4 is shared with other ISP customers

and I want to use dynv6 to map the domain to my homeserver
but when I use the update from the instructions my local static part of is everytime overwritten
so I tried this here so only my public prefix is overwritten
but this does not update my records at all :c what am I doing wrong?<domain>&token=<username>&ipv6prefix=<ip6lanprefix>

And I have AAAA Record with the static local part of my homeserver conncted directly via LAN to the FritzBox
and it is combining them correctly as far as I can tell (Public IPv6 prefix and static local part of my server)
But with<domain>&token=<username>&ipv6prefix=<ip6lanprefix> it doesnt update anything automatically, what am I doing wrong?

Look at this:

The Fritzbox only updates the prefix together with an IPv4 update. Unfortunately…