403 Forbidden Error when processing requisition into a PO using API

Summary:

We are trying to create a PO from requisition using Process Requisition Lines into a New Order API, however, we are hitting the wall with 403 forbidden error.

The interface user account has all the roles and privileges necessary for integration. Just wondering what are we missing. Our sample payload is like the below

{
    "ProcurementBU": "Vision Corporation",
    "RequisitioningBU": "Vision Corporation",
    "Type": "New Order",
    "Supplier": "Seven Corporation",
    "lines": [
        {
            "RequisitionLineId": 300100542878364
        }
    ]
}

Content (please ensure you mask any confidential information):

NA

Version (include the version you are using, if applicable):

26B

Code Snippet (add any code snippets that support your topic, if applicable):