(a legacy version of RealVNC), license keys are no longer issued or supported through traditional means as the software has transitioned to the RealVNC Connect subscription model Where to Find Your Existing License Key

If you previously purchased a perpetual license for VNC 5.x, you can retrieve your details via these official methods: RealVNC Account Portal : Log in to the RealVNC Deployment page

to view offline license keys associated with your historical purchases. Windows Registry