wp_generate_password returns password but can't login using it
require_once( ABSPATH . WPINC . '/registration.php' );
$user_pass = wp_generate_password();
$userdata = array(
  'user_pass' => $user_pass,
  'user_login' => esc_attr( $_POST['user_email'] ),
  'user_email' => esc_attr( $_POST['user_email'] ),
);

if( !$userdata['user_login'] )
  $error .= __('An Email Address is required for registration.', 'frontendprofile');
elseif ( username_exists( $userdata['user_login'] ) )
  $error .= __('Sorry, that Email Address is already in use for another account.', 'frontendprofile');
elseif ( !is_email( $userdata['user_email'] ) )
  $error .= __('You must enter a valid Email Address.', 'frontendprofile');
elseif ( email_exists( $userdata['user_email'] ) )
  $error .= __('Sorry, that Email Address is already for another account.', 'frontendprofile');

else{
  $new_user = wp_update_user( $userdata );
}