There may be an Insight knowledge agent that is not running.
Verify that the Insight network service is running on the machine where the agent is located:
For Windows, check the Network Service under Administrative Tools/Services
For Unix, type uv_net_svc
If the service is not started:
For Windows
Use the Windows Services panel
Find the CA Unicenter Insight Service
Right click on the service and choose Start
For Unix:
Type udmstart