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 91.214.84.252.sky-net.com.ua is not the root of its zone.
Instead, try zone transfer on sky-net.com.ua .
Instead, try zone transfer on sky-net.com.ua .