Connection to client virus chest

When I try to connect to certain client virus chests, I get: RPC server is not available. It’s not clear as to whether we’re talking about the server or the client, BUT the RPC server is both automatic and started/running on both machines. What else can I look at to see why the communication isn’t happening? I DO have communication to some boxes but not all. Thanks.

This is most likely the result of a communication or permissions issue.
Disable any firewalls (at least for troubleshooting purposes) and ensure you’re using sufficient credentials.