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 pl798k5vj18sri3a2nq1sg1bm6vs54bt.mailcloud.dk is not the root of its zone.
Instead, try zone transfer on mailcloud.dk .
Instead, try zone transfer on mailcloud.dk .