: If the filter stays "disabled" even after the network is fixed, the admin logs into the Kerio console via
Inspect outbound connectivity and firewall rules
💡 If the filter deactivates frequently, check your internet link speed. Slow links can trigger the "unreliable" flag, which the SSH fix above permanently ignores. Using Kerio Control Web Filter
: The default ISP DNS servers might be throttling requests from the filter, which makes frequent calls to services like for page ratings. License Hiccups : If the filter stays "disabled" even after
Kerio sends automated check queries to cloud infrastructure. If a response is dropped 10 consecutive times within 1 minute, the firewall marks the backend engine as unreliable and completely disables categorization.
If the UI is unresponsive or the filter refuses to activate despite a valid license, a service restart via SSH or the local console often resolves the "stuck" state.
If the licensing is correct and network connectivity is verified, a corrupted local database file may be blocking the service from starting. Clearing this cache forces Kerio to download a fresh categorization architecture. License Hiccups Kerio sends automated check queries to
Ensure your WAN interface has valid, working DNS servers (e.g., or ISP provided).
If the filter remains disabled due to network instability, you can manually disable the "Reliability" check.
The Kerio Control web filter is an essential feature that helps to protect networks from malicious and non-productive websites. When the web filter is not activated, and categorization is disabled, it can lead to security risks and decreased productivity. By following the steps outlined in this article, administrators can fix the issue and ensure that the web filter is working correctly. Regularly updating the Kerio Control software and categorization database can help to prevent such issues in the future. If the licensing is correct and network connectivity
Connect to your firewall appliance using an SSH client (like PuTTY).
Reproduce and verify
Check for the absence of "Invalid authorization" or "Unable to categorize" entries.