Open the Start menu, type , and press Enter.

for your specific antivirus software.

A simple reboot clears temporary system glitches, including network configurations and cached processes that might be interfering with license validation. You'd be surprised how many license errors disappear after a fresh restart. While you're at it, ensure that all available Windows updates are installed, as outdated operating system files can also cause unexpected permission and connectivity problems with Lumion's installer and license servers.