Before diving into the solutions, use this checklist for a quick diagnostic overview:

Some Web Filter issues are resolved in newer releases. Check for updates and apply the latest stable version. Always review release notes for known Web Filter fixes.

| Cause | Description | |-------|-------------| | 1. No valid license | Web filtering requires an active, non-expired license. | | 2. Disabled categorization engine | The feature is toggled off in configuration. | | 3. DNS resolution failure | The appliance cannot resolve categorization server hostnames. | | 4. Firewall rules blocking the appliance | Outbound HTTPS (port 443) to GFI/McAfee servers is blocked. | | 5. Proxy configuration missing | Kerio Control needs upstream proxy settings to reach cloud servers. | | 6. Time/date mismatch | SSL certificate validation fails if system time is incorrect. | | 7. Corrupted local cache or database | Stale categorization data prevents reinitialization. |

: Use Cloudflare (1.1.1.1) or OpenDNS (208.67.222.222) as custom DNS servers specifically for *.zvelo.com domains.

Usually 1–5 minutes. Restart the firewall engine for immediate effect.

Yes, but only with static URL lists, IP-based rules, or by disabling web filtering entirely. Dynamic filtering will not work.

Is your Kerio Control showing an "Invalid Authorization" error specifically, or is it just stuck in a "Disabled" state without further detail? Using Kerio Control Web Filter

After restarting, verify that the error log entry is no longer generated and that the Web Filter appears as activated in the Webadmin interface.

If you are experiencing, or have recently experienced, this issue, what specific error message appeared in your Security logs? I can provide more specialized troubleshooting steps based on that message. AI responses may include mistakes. Learn more

: Disable "Categorize each page regardless of URL rules" unless you need statistics – full categorization can decrease performance. This option should be enabled only if you intend to keep category statistics.