Hi Bob, thanks for the comment.
I can reproduce the condition you describe by selecting the Down icon in the icon bar above the map. This displays only down devices in Device Notifier (and also in List) view. Clicking that icon - it's a red square to the left of the red diamond with an excamation point in it - should clear the filter and let you look at all device states on the map simultaneously.
Selecting or clearing notifications for any of the states for all map devices is done by holding down the Alt key and clicking on the column.
Please let me know if this isn't the issue and we'll continue offline.