Purchase Order (PO) sent from Ariba Buying & Invoicing (P2P) is failing in SAP Integration Suite, managed gateway for spend management and SAP Business Network with the following error:

org.apache.cxf.binding.soap.SoapFault: Error reading XMLStreamReader: Unexpected character 'j' (code 106) in prolog; expected '<' at [row,col {unknown

1. Expired certificate on ERP or S/4 HANA side.
2. Configuration issues in Cloud Connector.
3. Not-unique Location ID set in Cloud Connector.

1. Check if the certificates are expired on ERP or S/4 HANA. If any certificate is expired, renew it. You can use this link for more information on how to renew the certificates: How to Maintain Certificates
2. Do a test in CIG Connectivity Tool to test the connectivity between Managed Gateway for Spend&Network and S/4 HANA or ERP and if it fails one of the possible issues is with Cloud Connector. To correct this, refer to Managed Gateway for Spend&Network Installation Guide to review the Cloud Connector configuration: Configuring Cloud Connector
3. Maintain a unique LOCATION ID which wouldn't be used by another customer. You can use your company name or part of it as part of the LOCATION ID to make it unique. Avoid single common words like ARIBA, CIG, etc.

This kind of error may happen with other document types as well, not just PO.

SAP Integration Suite Managed Gateway > Managed Gateway for Procurement