Getting empty feed

Hi, just need some help I tried to use the sample code for excluding products but after using it I’m getting no result on our feed. Even going directly on the core code removing the options for other product types still getting empty feed. Any thoughts? What am I doing wrong here.

switch ( $product_type ) {
case ‘composite’:
return $this->process_composite_product( $woocommerce_product );
break;
default:
break;
}