You may find that a service has failed and not been restarted. This article covers how you can enable monitoring for a service so that cPanel automatically restarts it.
1) Login to WHM as the root user, and navigate to the following location.
Home »Service Configuration »Service Manager
2) Under the "Monitor" column add a checkmark for the service that you would like to enable monitoring for
3) Click the blue Save button at the bottom of the page