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 ua-19.metrooptic.com.163.21.50.in-addr.arpa is not the root of its zone.
Instead, try zone transfer on 50.in-addr.arpa .
Instead, try zone transfer on 50.in-addr.arpa .