Hi @kris.backus,

What response are you getting. Your request query seems to work fine, and is able to procide me with the list of chain constituents

{
 "RetrieveItem_Response_3": {
  "ItemResponse": [{
    "Item": [{
      "RequestKey": {
       "Name": ".AV.TO",
       "Service": "IDN",
       "NameType": "RIC"
      },
      },
      "Status": {
       "StatusMsg": "OK",
       "StatusCode": 0
      },
      "Fields": {
       "Field": [{
         "DataType": "Int32",
         "Name": "PROD_PERM",
         "Int32": 84
        }, {
         "DataType": "Int64",
         "Name": "NUM_MOVES",
         "Int64": 93
        }, {
         "DataType": "Int32",
         "Name": "REF_COUNT",
         "Int32": 14
        }, {
         "DataType": "Int32",
         "Name": "RECORDTYPE",
         "Int32": 117
        }, {
         "DataType": "Utf8String",
         "Name": "LONGLINK1",
         "Utf8String": "APHA.TO"
        }, {
         "DataType": "Utf8String",
         "Name": "LONGLINK2",
         "Utf8String": "DBO.TO"
        }, {
         "DataType": "Utf8String",
         "Name": "LONGLINK3",
         "Utf8String": "YRI.TO"
        }, {

...

Hello @kris.backus

I confirms my colleague replication result. I can request data with your JSON request message via Postman, cURL successfully.

Did you get any error response message?