Support will guide you through what might be needed from the client machine if you speak to them.
To make a diagnosis do the following from the client machine:
A.- Ping the ePO server to see if it replies.
B.- trace the ePO server to verify routing.
C.- Validate trough telnet that your client/server ports respond on the ePO server, and from the server to see if the client responds.
the agent log is the one called "agent_MACHINENETBIOSNAME.log"
the agent update log is called "UPDATERUI_MACHINENETBIOSNAME.LOG"
Depending on your OS, the location is different, most commonly inside the documents and settings user folder, inside either program data or local data.
I Hope it helps,
With respect to the MER tool mentioned please read support article:
KB59385 - How to use MER tools with supported McAfee products