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 c3in34c6sajjhhotcdminq3cs46oicam.mailcloud.dk is not the root of its zone.
Instead, try zone transfer on mailcloud.dk .
Instead, try zone transfer on mailcloud.dk .