PayPal onApprove not calling ajax function

I'm trying to add a boolean to the database when the payment is successful.

  <script>
paypal.Buttons({
  createOrder: function(data, actions) {
    // This function sets up the details of the transaction, including the amount and line item details.
    return actions.order.create({
      purchase_units: [{
        amount: {
          value: '0.01'
        }
      }]
    });
  },
  onApprove: function(data, actions) {
    // This function captures the funds from the transaction.
    return actions.order.capture().then(function(details) {
      // This function shows a transaction success message to your buyer.
      alert('Transaction completed by ' + details.payer.name.given_name);
      $.ajax({
        url: "includes/payment_db.php",
        success: function(data) {
          alert('Successfully called');
        },
        error: function(jqxhr, status, exception) {
          alert('Exception:', exception);
        }
      });
    });
  }
}).render('#paypal-button-container');