Without a valid key, the anti-virus databases freeze. You are now running 3-month-old signatures against zero-day malware. This is worse than having no antivirus because it creates a false sense of security.
Troubleshooting
Kaspersky Endpoint Security (KES) uses a dual-method system for license validation: an (a 20-character alphanumeric string) used to register the product, and a License Key (a unique 32-character hexadecimal string) that is automatically generated to identify your specific installation. Licensing Tiers & Pricing (2026 Estimates) kaspersky endpoint security license key