One client can't update its virus definitions

Problem: One of my server can't update its virus definitions about 7 days ago

First, the setup of my Symantec Endpoint Protection Manager  was they are not using the default Management Server for the live update, all client gets their new virus definitions in internet but the SEP Manager distributes the command to the client to update its virus definitions. My problem was, one of my server cannot update it virus definitions about 7 days ago today, that the server where the Symantec Endpoint Protection Manager was installed. Anyone can give me advise what possible reason or solution why that server can't update its virus definitions?

Thanks a lot for who's gonna gave their helping hand in my case.