Sage 200 Professional API - Set Nominal Reference/Cost Centre/Department against sop_order_lines?

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Hi,

I'm trying to post a sop_order via the Sage 200 API, passing the sop_order_lines and nominals.

The sop_order and sop_order_lines are successfully created, but the nominal reference/cost centre and department do not set as per the values passed in the POST request, but instead the default values are taken from the account.

For example:

"Lines": [
    {
      "Code""TEST-001",
      "Description""Test Product 1",
      "Line_Quantity"1,
      "Line_Type""EnumLineTypeFreeText",
      "Nominal_Cost_Centre""UKI",
      "Nominal_Department""",
      "Nominal_Reference""4680",
      "Selling_Unit_Price"10,
      "tax_code_id": 4650,
      "unit_discount_overridden"true,
      "unit_discount_value"0
    }
]
I've been referring to the document here for sop_orders:
...and for sop_order_lines
The nominal combination of exists and can be added fine when manually added to a free text line item via Sage 200 client, but when this is attempted via the API, it does not set correctly. I've also noticed that the  attributes "Nominal_Cost_Centre", "Nominal_Department" and "Nominal_Reference" are not returned from the post response or from a GET response when returning an existing sop_order_line
I am wondering whether this is because we are not currently testing against the latest version of Sage?
At the moment, we are using Version 12.00.0041 - wondering if this will only work for Sage 200 2022 R1 (Version 12.00.0046)? If we are unable to move to the latest version, is there another method by which these can be set, or would upgrading be the only option?
Thanks
Jon