The filter relies on DNS queries to categorization servers. If these queries time out 10 times in a row, the filter will auto-disable for reliability.

Switch your firewall's custom DNS servers to more reliable ones like Cloudflare 208.67.222.222 ) to ensure *.zvelo.com URLs can be resolved. Restart the Kerio Control Engine

: Kerio Control sends automatic DNS check queries to its update servers. If these fail 10 times in a row within one minute, the system deems the filter unreliable and disables categorization.

When Kerio Control displays the error "Web Filter is not activated" or "categorization is disabled," it typically indicates a breakdown in communication between your firewall and the categorization servers or an expired license component . This effectively disables category-based filtering rules, leaving your network exposed. Primary Causes and Solutions