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 128.121.88.208.in-addr.arpa is not the root of its zone.
Instead, try zone transfer on 208.in-addr.arpa .
Instead, try zone transfer on 208.in-addr.arpa .