The phrase "not working" can be used as an adjective, for example:
My laptop is not working.
What is the noun-form of the adjective "not working"?
E.g. "The not-workingness of my laptop."
You could put a few options
"Brokenness" would be my first choice
"Dysfunctionality" would also work
"Failure" could work depending on the context too.
Inoperability could be added to the list of candidates.
Granted, in medicine, inoperable describes being unsuitable for surgury without undue risk (as in, an inoperable tumor).
However, inoperability has another meaning; which Collins describes as the state of being unworkable, or incapable of being operated. TFD lists it as the noun form of inoperable, which means not functioning or inoperative.
I like J.R.'s Inoperability. I might also suggest:
Malfunction could be used, but it may suggest a compromise of functionality that is less than total.