Error message in Open Interface Rest Web Service

Hello,

I'm following this document (https://docs.oracle.com/cd/E26401_01/doc.122/e20927/T511473T669558.htm#isgdg_oitpost) to use "Open Interface : Material Transactions Interface Manager" but when I try to run the POST method it returns the following error: 

<?xml version = '1.0' encoding = 'UTF-8'?>

<OutputParameters xmlns="http://xmlns.oracle.com/apps/inv/concurrentprogram/rest/mtl_transactions/mtl_transactions_interface">

  <Summary>

  <SuccessCount>0</SuccessCount>

  <ErrorCount>1</ErrorCount>

  </Summary>

  <Result>

  <Output>

  <Index>1</Index>

  <Status>FAILURE</Status>

  <Message>Run time error.. Please see service log for detials</Message>

  <MTL_TRANSACTIONS_INTERFACE_REC>

  <TRANSACTION_INTERFACE_ID>99988866</TRANSACTION_INTERFACE_ID>

  <INVENTORY_ITEM_ID>210135</INVENTORY_ITEM_ID>

  </MTL_TRANSACTIONS_INTERFACE_REC>

  </Output>

  </Result>

</OutputParameters>

However I can use the GET, PUT and DELETE methods without any problem. I attach the payload file used.

Kind regards