Move SEP Client from 12.1.1 SEPM to 12.1.6 SEPM

I want to move 300 SEP Clients from 12.1.1 SEPM to 12.1.6 SEPM. We have 2 Management servers.
Symantec support suggested to try Sylink Replacer or Remote Push after enable Computer Browser service in SEPM and Remote Registry service in SEP endpoint. I have done both and verified all needed Network ports are open.
But, I am still unable to update the SEP 12.1.1 client to communicate with 12.1.6 SEPM server.
I already logged case with Symantec Support but not helpful. Please help.