Products per page won't change

Trying to get at least 16 products on the category page. (4×4)
I have made following changes already to functions.php

// Change number or products per row to 4
add_filter('loop_shop_columns', 'loop_columns');
if (!function_exists('loop_columns')) {
	function loop_columns() {
		return 4; // 4 products per row
	}
}

// Redefine woocommerce_output_related_products()
function woocommerce_output_related_products() {
woocommerce_related_products(4,1); // Display 4 products in rows of 4
}

//NUMBER OF PRODUCTS TO DISPLAY ON SHOP PAGE
add_filter( 'loop_shop_per_page',  create_function( '$cols', 'return 24;' ), 20 );

For some reasons, I won’t get more than 5 products per page (4 wide)

see website here

(WP multiusersite)
(own custom theme with woocommerce plugin added.)

any help would be appreciated.

http://wordpress.org/extend/plugins/woocommerce/