Changes since SOA version
IXFR is a zone transfer request that returns changes since a specific SOA version. Enter the SOA version to request changes since then.
Not an apex domain
The domain cu0pg6cnnkbpb4hnarj0jm52qkbe3jvs.letsvisualize.dk is not the root of its zone.
Instead, try zone transfer on letsvisualize.dk .
Instead, try zone transfer on letsvisualize.dk .