Stopped working

Was working fine, but now items are added to cart but no coupon is applied

link is: /shop/cart?fill_cart=50×9&apply_coupon=code

older method still works though i.e.
/shop/product/prod_name/?add-to-cart=9&quantity=50&apply_coupon=code

https://wordpress.org/plugins/soft79-cart-links-for-woocommerce/