| Possible Cause | Resolution |
|---|---|
| The agent control service is not running. | Start the agent control service. |
| A port mismatch occurs (the port that the agent control service is listening to and the port at which the controller wants to connect the agent control service are different). | Adjust the agent connection settings. |
| The agent is connected through a proxy and the proxy is down. | Check the agent connection settings and restart the proxy. |