multiple values in an array for category__and does not work with WP_Query

Changing:

$args = array (
              'category__and'                    => $cats
        );

to:

$args = array (
                  'category__in'                    => $cats
            );

Does the trick.

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)