You can reactivate any alert that was previously closed. After you reactivate an alert, it is once again displayed in the default view of the Alerts page of System Center Advisor.
To reactivate an alert
In the Advisor portal, click the Alerts icon.
Filter the list to show only closed alerts. To change the filter, click the checkmark next to Status and then select Closed, or both Closed and Active, and then click Apply.
The list of alerts is updated to include closed alerts.
Select one or more alerts that you want to reactivate, and then click Activate.