you need to have at least a 10.0 server to support and manage 10.x clients.
the reason for this is that with 10.0, we switched communication to use secured TCP. While a SAV10 server is capable of managing all versions of client (as it can support both UDP and TCP), the SAV10 client has to be managed by a SAV10 server as its only form of communication is TCP.
If you upgrade your server 10.1.5 then it will enable this "legacy" option and you will be able to use it to manage both SAV8 and SAV10.