You are creating sales orders via web service and using External Payment as Payment Method. When you trying to update the Discount via web service, you find system does not add the discount into the sales order.
Reproducing the Issue
It is an internet order, you firstly create the sales order via the web service with External Payment information and system successfuelly creates the order.
Then, you execute the second web service to update the order discount, however the discount is not able to be updated in the order.
Note, it works fine if External Payment is not used in the first creation web service.
For external payment sales order there is no possibility to change the price components.
This is expected system behavior.
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