Como declarado em depreciação do NPAPI: guia do desenvolvedor :
In April 2015 (Chrome 42) NPAPI support will be disabled by default in Chrome and we will unpublish extensions requiring NPAPI plugins from the Chrome Web Store. All NPAPI plugins will appear as if they are not installed, as they will not appear in the navigator.plugins list nor will they be instantiated (even as a placeholder). Although plugin vendors are working hard to move to alternate technologies, a small number of users still rely on plugins that haven’t completed the transition yet. We will provide an override for advanced users (via chrome://flags/#enable-npapi) and enterprises (via Enterprise Policy) to temporarily re-enable NPAPI (via the page action UI) while they wait for mission-critical plugins to make the transition. In addition, setting any of the plugin Enterprise policies (e.g. EnabledPlugins, PluginsAllowedForUrls) will temporarily re-enable NPAPI.
Então, o April chegou e o Google Chrome desativou os plug-ins NPAPI, incluindo o Java.
Como reativá-los em máquinas Windows?