3558613 - WrapperException when retrieving data with OTTER in PI/PO

Have updated to the newest ELSTER ERiC version according to SAP Note 3522925 - ETNotif, ETStmt, ELStAM: New ELSTER ERiC Version 4:

• PI/PO - Process Integration/Process Orchestration
  SAP Note 3546333 - Changes for 2025 for Elster/PI - with ERiC 41.2 provides the patch.
  Before you import the patch using ERiC 41, implement SAP Note 3487893 (ETStmt, ELStAM: New version of data retrieval for ELSTER ERiC Version 40 or 41) in your system.

Normal ELSTER Transfer is working fine, like Employment Tax Notification, Employment Tax Statement etc.
But when trying to fetch some Data for the new OTTER Transfer, the below error is thrown:

"WrapperException is caught whlile processing the message:
[EXCEPTION]
com.sap.fin.eric.wrapper.exception.WrapperException: receiveOttoDataInLoop()Error while receiving data from Otto"

An XPI Inspector trace with example 71 (Elster) shows the following logs:

"Proxy: URL=xxx, User=nicht gesetzt, Pass=nicht gesetzt, Auth=nicht gesetzt
URL gesetzt: https://objektspeicher.elster.de:443/api/v1/obj/xxx
}} OttoEmpfangBeginnen = 0
{{ OttoRueckgabepufferErzeugen
}} OttoRueckgabepufferErzeugen = 0
{{ OttoEmpfangFortsetzen
Starte Transfer
Proxy HTTP-Statuscode 403"

• SAP NetWeaver 7.5
• SAP Process Integration
• SAP Process Orchestration

Process Integration, PI, Process Orchestration, PO, NetWeaver, XI, AEX, OTTER, Elster, ERiC 41, ERiC, ETStmt, ELStAM, receiveOttoDataInLoop, WrapperException , KBA , BC-XI-CON-ELS , HR/FI Elster Module for PI , PY-DE-FP-E2 , ELStAM Verfahren , PY-DE-FP-LSB , Employment tax statement , PY-DE-BA , Business to Administration , Problem