From my experience it means that the action has never been executed, so you either never specified it in your Next action or, more commonly, its never enabled due to an error in your spec.
On Thursday, April 25, 2019 at 1:35:46 PM UTC+2, xiaoq...@xxxxxxxxx wrote:
In this websites https://tla.msr-inria.inria.fr/tlatoolbox/doc/model/results-page.html, it shows that indicates an error in the spec. So what kind of error? I am stucked here.