Vesta roundcube mail login failed

Check both 1. Roundcube error log in /var/log/rouncubemail/error.logEroor: rcube imap.php on line 202 (POST /webmail/?_task=mail&_action=login 2. Dovecot error log in / var/log/maillogauth: Error: passwd-file: open(/etc/dovecot/users)this error...