I'm sorry but i'm stuck since a lot of time now.
I tried to make a scope for ipv6 at my home, i have a windows server 2019 machine that manages a lot of things.
I don't understand why but i can't have something good, my router from my provider seems to give all ipv6 even when i (think) disable ipv6 dhcp (it's not clear, this box has more than 10 years).
I tried with fc and fd ranges, my server uses a static ip like for ipv4... everything is ok for ipv4 but it don't work at all with ipv6