Another angle: maybe they upgraded from an older OS and the digital license is still linked through their Microsoft account. Suggesting to sign in with their account could help recover the license. But if the build is very old, maybe the migration path to a newer Windows version is better, though not feasible here since the user specifically wants activation.
Busca "Cmd", haz clic derecho y selecciona . Escribe slmgr.vbs -ipk y presiona Enter. Activación Telefónica : clave para activar windows 8 single language build 9200 240
Guía de Activación: Windows 8 Single Language (Build 9200) Another angle: maybe they upgraded from an older