Kerio deactivates the filter if 10 consecutive DNS queries fail within one minute. Usually, it tries to re-enable itself after one hour, but a manual restart is often faster. 2. Resolve "Invalid Authorization" Failures
The error typically occurs when the firewall cannot reach the Zvelo categorization servers or when the license token has expired. This is often triggered by DNS failures, where the system marks the filter as "unreliable" after multiple failed connection attempts. Core Troubleshooting Steps 1. Verify DNS and Reachability
Sometimes a simple reboot after changing DNS settings is required to force a new token request. 3. Advanced SSH Fix (Disable Reliability Detection)
Kerio Control uses DNS queries to reach its update and categorization servers. If your ISP or current DNS configuration is slow or blocking these requests, the filter will deactivate.
Ensure your Kerio Control Web Filter license is active. Without a valid subscription, the module defaults to a trial state and eventually disables itself.
Note that the Web Filter is disabled by default for the Guest Interface to allow users to reach the welcome page without authentication.
For categorization to work accurately on secure sites, ensure HTTPS Filtering (decrypt and filter) is enabled under Content Filter > HTTPS Filtering .
If the filter keeps disabling due to minor network fluctuations, you can disable the "Reliability Detection" feature via the Kerio Control Console: Connect to your Kerio Control appliance via . Navigate to the directory: cd /opt/kerio/winroute .
Avoid using Google DNS (8.8.8.8) for Zvelo categorization as it can cause "Invalid Authorization" errors. Instead, use Cloudflare (1.1.1.1) or OpenDNS (208.67.222.222).
Web Filter categorization disabled. Serial number: ko-197974