Refunds to Kaufland

The refund or cancellation is carried out via event action.

Checking the logs:

Integration: PlentyLegacy\Modules\EventSystem
Identifier: Kaufland
Reference type: orderID
or
Reference type: externalOrderId
Reference value: your order ID (orderId) or the external order ID (externalOrderId)

Successful messages are displayed under level:info. 
Error messages are consequently under level:error.

If you find an error log, check whether your refund may already have been processed previously on Kaufland. The refund/cancellation request can only be sent to Kaufland if it has not yet been carried out.

Error messages: errorCode:400 errorMessage:Validation Failed

The message looks as follows:

Object
requestURL:"https://sellerapi.kaufland.com/v2/order-units/314567919523486/cancel"
errorCode:400
errorMessage:"{\"message\":\"Validation Failed\",\"errors\":[]}"
Trigger:"backend: POST /rest/orders/796239/returns"

If the cancellation has not already been reported directly to Kaufland beforehand, the event action for the cancellation should be executed again. If this does not lead to the desired result, please feel free to report your issue in a (preferably existing) topic with the order ID.

You can find out what a recommended event action looks like here:
Automatically sending cancellations