The Sage key file issue occurs when there are some files missing from the Shared Documents folder or because some malware has infected your system. You can uninstall and then reinstall Sage 50 to fix ‘Key File not Found’ or ‘Bad Key File.’ Have a look at the steps given below to find out how to reinstall Sage 50: • Step 1: Open the main ‘Control Panel and go to ‘Programs and Features.’ • Step 2: Look for Sage in the list of installed programs and click ‘Uninstall.’ • Step 3: Go to the Sage website and download the installation file. • Step 4: Double-click the Sage 50 EXE file and follow the prompts to reinstall Sage on your computer. If you have any trouble completing the installation steps, you can call the Sage tech support number and ask for assistance.