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 sdtc.ar03.s3-0-0-100.network.21741.americanis.net is not the root of its zone.
Instead, try zone transfer on americanis.net .
Instead, try zone transfer on americanis.net .