If the System Agent could not communicate with CA (dSeries) Workload Automation Server, you can issue 'listagent' command from the Command Line Interface (CLI) on the Desktop Client to check the Agent status or check the content of 'status' and 'status.os' files (located in the Agent installation directory). The latter would provide additional information about the Agent, including the last Agent start information.
In order to diagnose the problem, you can check the following;