Add to Cart Button Not Translating on Submission – Magento Solution

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/";
                                    }
                                 });

you could try to set the product param to false and then set the return_url param:

$observer->getRequest()->setParam('product', false);
$observer->getRequest()->setParam('return_url', $this->_redirect->getRefererUrl());
$this->_messageManager->addError(__('This product cannot be added to your cart.'));

The cart controller checks if the product param is set here: https://github.com/magento/magento2/blob/2.0/app/code/Magento/Checkout/Controller/Cart/Add.php#L99

and if it is not, it calls goBack. the goBack method checks if you made an ajax request (I think you did) and then returns an additional param backUrl in the ajax response.

https://github.com/magento/magento2/blob/2.0/app/code/Magento/Checkout/Controller/Cart/Add.php#L165

The getBackUrl method then returns the return_url param:

https://github.com/magento/magento2/blob/2.0/app/code/Magento/Checkout/Controller/Cart.php#L113

===UPDATE===

ok since the message adding does not work here, you should try another way (it's also more straight forward)

create a Plugin to Intercetp before this function: https://github.com/magento/magento2/blob/2.0/app/code/Magento/Checkout/Model/Cart.php#L341

If you do not want your product added, just throw an Exception with the desired Message. You find a nice tutorial for creating plugins here: http://alanstorm.com/magento_2_object_manager_plugin_system

The Product adding should be interrupted and the Exception should be rendered as message https://github.com/magento/magento2/blob/2.0/app/code/Magento/Checkout/Controller/Cart/Add.php#L137

add the following type to your modules etc/frontend/di.xml

<type name="Magento\Checkout\Model\Cart">
    <plugin name="interceptAddingProductToCart"
            type="Vendor\Module\Model\Checkout\Cart\Plugin"
            sortOrder="10"
            disabled="false"/>
</type>

Then the class Vendor/Module/Model/Checkout/Cart/Plugin should look like this:

<?php
namespace Vendor\Module\Model\Checkout\Cart;

use Magento\Framework\Exception\LocalizedException;

class Plugin
{
    /**
     * @var \Magento\Quote\Model\Quote
     */
    protected $quote;

    /**
     * Plugin constructor.
     *
     * @param \Magento\Checkout\Model\Session $checkoutSession
     */
    public function __construct(
        \Magento\Checkout\Model\Session $checkoutSession
    ) {
        $this->quote = $checkoutSession->getQuote();
    }

    /**
     * beforeAddProduct
     *
     * @param      $subject
     * @param      $productInfo
     * @param null $requestInfo
     *
     * @return array
     * @throws LocalizedException
     */
    public function beforeAddProduct($subject, $productInfo, $requestInfo = null)
    {
        if ($this->quote->hasData('custom_attribute')) {
            throw new LocalizedException(__('Could not add Product to Cart'));
        }

        return [$productInfo, $requestInfo];
    }
}