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 listserv2-public.it-prod-cots.aws.umd.edu is not the root of its zone.
Instead, try zone transfer on it-prod-cots.aws.umd.edu .
Instead, try zone transfer on it-prod-cots.aws.umd.edu .