openstudio-server: when is an analysis status = na?

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In looking through the openstudio-server code, it seems like there are four possible status enumerations for any datapoint:

completed: which means it is done with that datapoint queued: which means it is in the pipeline to run started: which (i think) means the simulation is in progress but not completed na: ???

when would you get an na? And is this a good sign that you should abort the entire analysis?