There is a troubleshooting article - https://techdocs.broadcom.com/us/en/ca-enterprise-software/intelligent-automation/ca-workload-automation-de/12-4/troubleshooting/troubleshooting-agent-down/agent-showing-inactive.html
The port for the DE manager is not open or accessible from the agent's machine (default 7507)
The DE tracelog may display the following message.
XX/XX/20XX 00:00:12.345 [dm:communications:exception] [ERROR] DM.OutputMessageQueue.AGENT1: [20XX-XX-XX_00:00:12.345] Exception caught sending to AGENT1: The conversation is unable to connect to partner agent1:7520.
The exception is Connection timed out (Connection timed out).
Ensure to open the port for the WA Manager.
Hope it helps!