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 ip56.ip-135-125-177.eu is not the root of its zone.
Instead, try zone transfer on ip-135-125-177.eu .
Instead, try zone transfer on ip-135-125-177.eu .