This study develops a practice-relevant theory explaining why some information technology (IT) unavailability incidents lead to severe and prolonged organizational consequences. By redefining IT unavailability as unmet demand for IT resources rather than simple system downtime, the paper shows how disruptions cascade through information capacity deficits and business capacity deficits, ultimately impairing critical services, affecting clients, and damaging organizational reputation. An analysis of 28 real-world IT unavailability incidents reveals that three reinforcing feedback loops (IT inertia, information inertia, and business inertia) can intensify service disruption, delay recovery, and amplify downstream impacts.