Magento 2 Shopping Cart Not Clearing – Troubleshooting Guide

Try one thing:

• Load product by product id ($_product->getId()).

  $product = Mage::getModel("catalog/product")->load($_product->getId());

• Then use:

$product instead on $_product in onclick. Code is below:

onclick="setLocation('<?php echo $this->getAddToCartUrl($product) ?>')"

I hope, it will help.

Below is the updated code for working Add To Cart Url:

<div class="upsell">

<?php if (Mage::helper('checkout/cart')->getQuote()->getSubtotal() < 75.00)
{?>
 <h1><?php echo 'We see your subtotal is under £75, why not add these products to qualify for Free Delivery';?></h1>
 <br>
<?php

$categoryid = 1054;

$category = new Mage_Catalog_Model_Category();
$category->load($categoryid);
$collection = $category->getProductCollection();
$collection->addAttributeToSelect('*');



$collection->getSelect()->order(new Zend_Db_Expr('RAND()'));
?>
<div class="upsell_products">

<?php $i = 0; ?>

<?php foreach ($collection as $_product){ ?>
<?php $product = Mage::getModel('catalog/product')->load($_product->getId());?>


<div class="product">
<a href="<?php echo $_product->getProductUrl() ?>">

<div class="product_img_cart">

<img src="<?php echo $this->helper('catalog/image')->init($_product, 'small_image'); ?>" alt="<?php echo $_product->getName(); ?>" /></a>
</div>
<a href="<?php echo $_product->getProductUrl(); ?>">
<p class="upsell_pro_name"><?php echo $_product->getName(); ?></p>
<p class="upsell_pro_price"><?php echo Mage::helper('core')->formatPrice($_product->getPrice());?></a></p>
<div class="add_cart_btn">
<button type="button" title="<?php echo $this->__('Add to Cart') ?>" class="button btn-cart" onclick="setLocation('<?php echo $this->helper('checkout/cart')->getAddUrl($product)?>')"><span><span><?php echo $this->__('Add to Cart') ?></span></span></button>
</div>
</div>
<?php if($i++ == 3) break; ?>

<?php } }

I found out i had to add this to my script at the bottom of the page

jQuery.ajax({
                                    type:"GET",
                                    url:location,
                                    success:function(data){
                                         parent.window.location.href = "/checkout/cart/";
                                    }
                                 });