1) Restart agent service
2) flush health service state and cache of agent from Monitoring workspace --> Operations Manager--> Agent Details --> Agent health State --> agent state
3) use the folllowing for troubleshoot
1.Open the Operations console and click Monitoring.
2.Navigate to the Operations Manager\Agent Details\Agent Health State view.
3.In Agent State from Health Service Watcher, click the agent you want to check connectivity for.
4.In the Tasks pane, select the task Show Gray Agent Connectivity Data.
5.The Run Task Show Gray Agent Connectivity Data dialog box appears. Click Run.
6.The Task Status dialog box appears. When the task is completed, you can click Copy Text or Copy HTML and paste the task output in the appropriate tool for further review.
The task output will identify the following information:
The last time a heartbeat was received from the agent.
Whether the System Center Management Health service is running on the agent.
Whether the agent responds to ping.
The last time the configuration on the agent was updated.
Possible reasons that the agent is unavailable.
The management server that the agent reports to.
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