"Document does not exist" exception when updating a Purchase Order, Agentry

Hello Gurus,

I updated a PO in SAP by calling the Bapi. It displays the error:

com.syclo.sap.mm.steplet.POUpdateSteplet::throwExceptionToClient::1513::POUpdateSteplet - Document  does not exist |

I checked on SAP and found the PO there. And in the log file, the PONumber, Company code are sent to the server. Then  why It throws the above exception.

I spent a day but cannot find out what happen to the PO. Please help me. Thank you very much.

Edit: Even though I hard coded the PO Number, it still display the error.

JCO.Structure header = _imports.getStructure("IS_POHEADER");

  String poNumber = user.getString("transaction.PONumber");

  setValue(header, log, "PO_NUMBER", poNumber);

  String companyCode = user.getString("transaction.CompanyCode");

  setValue(header, log, "COMP_CODE", companyCode);

  String purchaseOrg = user.getString("transaction.PurchaseOrganization");

 

JCO.Structure headerX = _imports.getStructure("IS_POHEADERX");

setValue(headerX, log, "PO_NUMBER", poNumber);

setValue(headerX, log, "COMP_CODE", "X");