there is error happened when the add to cart end point (maybe https://benush.es/en/cart),we can't see the error information,
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there is errror in broswer console,
fbq('track', 'InitiateCheckout', {num_items: 0, content_ids'], content_type: 'product', value: 0, currency: 'EUR'});
please disable js compress and postion where the error happened