Still, also you will need to perform a cleaner-install, If you are getting" Key File Not Found Or Bad Key File When Opening Sage 50. You are better off making sure that Sage 50 is wiped from your system. After uninstalling by using Control panel> Programs and Features, use the Microsoft tool called" Fix problems that block programs from being installed or removed . Let’s check how to fix the issue key file not found or bad key file when opening sage 50. .