The Kerberos login failed due to a failure of the client to authenticate the user's principal with the KDC or a failure of the server to authenticate the client. The most likely causes are the Kerberos principal may not be signed in, the principal's ticket may have expired, or the client, server, or KDC's system time are not within a few minutes of each other. The LogFile connection parameter or the server's -z option may provide more information.