Every once in a while after a customer successfully completes a transaction on the payment provider environment (Adyen in this case), for some reason the webhook which is called fails to return a 200 response to Adyen, which in turn results in Adyen not notifying Umbraco/Vendr that the transaction was successful so that the cart can be 'promoted' to an order in Vendr with the subsequent flow being triggered. This means the order remains in the Carts section of Vendr instead of the Orders section, the customer does not receive the e-mail notifying them that their order has been received and most importantly of all, the order is not sent to the third-party CRM for actual real-world processing. I have spent hours debugging the code of Vendr and AdyenCheckout to try and decipher why this is going wrong and cannot find an explanation. It seems that the

AdyenCheckoutPaymentProvider

class method

ProcessCallbackAsync()

gets to the expression

if (adyenEvent.Success) { ... }

but this most likely results in

false

seeing as the code inside this

if

expression doesn't execute for these specific transactions. Inside this block is where

SendNotificationReceivedMessage()

is invoked, causing a 200 response with body

[accepted]

to be returned to Adyen, which is what they need to know that the webhook was executed successfully and in order to continue with finalizing the order via

NotificationEventHandlerBase.Handle()

. However, inspecting the event body in the Adyen webhook event logs shows that the

notificationItems

object does in fact state

success: true

, so I really don't understand why the above code isn't being triggered, no matter how many times I use the "Retry" button from within the Adyen Customer Area.