DSS REST API: Client is receiving this error: "EntitySetController Unmapped Request ErrorCode",

Can you please advise? Client is trying to set up an Entity List with the use of DSS REST API.

Request 1: {{protocol}}{{host}}{{api}}Extractions/EntityLists

@{ "@odata.type": "#EntityList",

"Name": "DITAppendIdentifiers"}

Response 1 :

{

"@odata.context": "https://selectapi.datascope.refinitiv.com/RestApi/v1/$metadata#EntityLists/$entity",

"ListId": "0x07bcacf8e8ad3273",

"Name": "DITAppendIdentifiers",

"Count": 0,

"Created": "2021-10-07T05:47:51.072Z",

"Modified": "2021-10-07T05:47:51.072Z"

}

Request 2: (URL{{protocol}}{{host}}{{api}}Extractions/EntityLists('0x07bcacf8e8ad3273')/ThomsonReuters.Dss.Api.Extractions.EntityListDITAppendIdentifiers)

0x07bcacf8e8ad3273 is list id generated from 1^st request.

{

"Identifiers": [

{

"Identifier": "12286",

"IdentifierType": "OrgId",

"UserDefinedIdentifier": "UserIdent4A"

}

],

"KeepDuplicates": false,

"IncludeParentAndUltimateParent": false

}

Response 2: http code : 501 Not Implemented

{

"error": {

"code": "EntitySetController Unmapped Request ErrorCode",

"message": "EntitySetController Unmapped Request ~/entityset/key/unresolved"

}