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 855466d9ebd74951a7571ae0aa970a15.v1.radwarecloud.net is not the root of its zone.
Instead, try zone transfer on radwarecloud.net .
Instead, try zone transfer on radwarecloud.net .