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 7ulgpaiajigj1qspm0tnvdajd75h8o5f.dbk.dk is not the root of its zone.
Instead, try zone transfer on dbk.dk .
Instead, try zone transfer on dbk.dk .