NPAPI (Netscape Plug-in API) is a cross-platform plugin architecture used by many web browsers, also serving the Check Point Deployment Agent that is used to deploy SSL Network Extender, Secure Workspace and the Compliance Scanner.
On March 7th 2017, Firefox build 52 was released, removing support for Netscape Plugin API (NPAPI).
Refer to sk113410 - Mobile Access Portal and Java Compatibility - New Mobile Access Deployment Agent technology that outlines Check Point's plan to deliver a new Mobile Access Deployment Agent technology.