Error in M2 Checkout

Question

I'm having a problem with product checkout in M2. When I want to place the order, a success page must be displayed, but I got redirected to the view cart page, and the item is still in the cart. I have traced it down to app/code/Magento/Checkout/Controller/Onepage/Success.php and find out this piece of code:

if (!$this->_objectManager->get('Magento\Checkout\Model\Session\SuccessValidator')->isValid()) {
        return $this->resultRedirectFactory->create()->setPath('checkout/cart');
    }

and in app/code/Magento/Checkout/Model/Session/Validator.php

    public function isValid()
{
    if (!$this->checkoutSession->getLastSuccessQuoteId()) {
        return false;
    }

    if (!$this->checkoutSession->getLastQuoteId() || !$this->checkoutSession->getLastOrderId()) {
        return false;
    }
    return true;
}

What could be the cause to this?