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 u-67ddx95lyjpbsv5-2a02-20.6bone.mynet.it is not the root of its zone.
Instead, try zone transfer on 6bone.mynet.it .
Instead, try zone transfer on 6bone.mynet.it .