The Error,
Warning and Debug logs are not available from the Kerio Personal Firewall's
user interface — they can only be opened as files in the Logs subdirectory of the directory where Kerio Personal Firewall is installed (typically C:\Program Files\Kerio\Personal Firewall 4\logs).
the file itself has the .log extension (e.g. error.log).
Errors which seriously affect functionality of Kerio Personal Firewall (i.e. the Personal Firewall Engine cannot be started) are logged into the Error log.