The monitor fails to connect to computers in the monitored resources list.
The status is Disconnected, as shown in the screenshot below -
Those computers are excluded from monitoring.
Please go to the folder, those computers reside in, right click it and choose properties.
In the properties window make sure to include the computers in the Monitor's resources.
By default all folders inherit the configuration from the root (top) folder.
If the folder is excluded by mistake, check the root folder properties as well.