I created a small script that receives an order transaction ID and must change the order status to PAID.
$tran_id = $_POST['transaction_id'];
$tran = \XLite\Core\Database::getRepo('\XLite\Model\Paymen t\Transaction')->findOneByPublicTxnId($tran_id);
$ord = $tran->getOrder();
This was working fine until we installed the Paypal Checkout payment method. If the Paypal Checkout method is active, we get the following error in the last line of our code (marked red):
Class 'PayPalCheckoutSdk\Core\PayPalHttpClient' not found
The transaction gets updated to SUCCESS fine, but the error when calling the flush() function prevents the order from being updated to PAID.
The order we are updating doesn't use the Paypal Chekout at all, it has nothing to do with Paypal.