As you can see in the following a host went down then came back up. I would assume since it cleared it would no longer show as an active alarm. Why is it not clearing itself in the active alarms?

Device Active and Responding	Unacknowledge	Clear	21 Sep 2016 10:26:45 PM EDT
Host NAME in LOCATION is not responding	Unacknowledge	Critical	21 Sep 2016 10:19:29 PM EDT