wp_signon( $creds, false ); not working

Hope this helps someone else. After hours of debugging, I found out that under multisite setup, wp_signon ($creds, false) will not log you in. So you should either do:

$user = wp_signon ($creds, false);
wp_set_auth_cookie($user->ID);

or

$user = wp_signon ($creds, true);