Reference Nbr API Error in Payment Details after upgrading to 2021R2

Hi,

We recently upgraded to 2021R2 and I am now unable to apply invoices to a payment via the API.

The invoice can be applied manually without issue.

I am seeing this error message:

"An error occurred during processing of the field Reference Nbr.: Reference Nbr. 'IN150421' cannot be found in the system.\nPX.Data.PXOuterException: An error occurred during processing of the field Reference Nbr.: Reference Nbr. 'IN150421' cannot be found in the system.",

This is the PUT command, using Default/17.200.001/Payment

{
  "ReferenceNbr":{"value":"013185"},
  "DocumentsToApply":[   
                    {
                        "AmountPaid": {"value" : "641.99" },
                        "DocType": {"value": "Invoice" },
                        "ReferenceNbr": {"value" : "IN150421" }
                    }
                   ]
}

Thanks in Advance for any help.