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 srv30403.dus7.dedi.server-hosting.expert is not the root of its zone.
Instead, try zone transfer on dus7.dedi.server-hosting.expert .
Instead, try zone transfer on dus7.dedi.server-hosting.expert .