It took myself and support (even including escalations) far too long to figure out that if an SNMP device has device availability turned off, it will not trigger alerts at all even if the monitored OID rules have been met.

The monitored OIDs should always be functional and alerts generated, even if device availability monitoring is turned off. For instance, I do not need an alert when someone turns the printer off, but I do need an alert if it is low on toner.