Error when trying to createmetadata using CreateFileMetadataAsync API

Hello,

I am trying to create metadata for file requests and I am seeing 404 not found error. I am not sure what is missing. Below is my code.

 var boxFileRequestObjectresponse = new BoxFileRequestObject();
            var boxhelper = new BoxHelper(_configuration);
            boxhelper.CreateClient(_configuration);
            var boxFileRequestId = _configuration.GetSection("BoxFileRequestId");            try
            {

            /Get khcnumber
                var destinationFolder = new BoxRequestEntity
                {
               // Box parent folder
                    Id = "159523690847",
                    Type = BoxType.folder                    
                };
                string khc = KHCNumber.ToString();
                var copyRequest = new BoxFileRequestCopyRequest
                {
                    Description = khc,
                    Folder = destinationFolder                    
                };
                var metadataValues = new Dictionary<string, object>()
                {
                    {"khcnumber",khc }
                };               
                boxFileRequestObjectresponse = await boxhelper.client.FileRequestsManager.CopyFileRequestAsync(boxFileRequestId.Value, copyRequest);

//Passing the boxFileRequestObjectresponse.Id as the field since the metadata needs to be created for that file.              

Dictionary<string, object> metadata = await boxhelper.client.MetadataManager                 .CreateFileMetadataAsync(boxFileRequestObjectresponse.Id, metadataValues, "enterprise", "khcFileinfo");

            }
            catch (Exception ex)
             { throw ex; }

            return Json(new { boxSharedLinkUrlResponse = boxFileRequestObjectresponse.Url }, new JsonSerializerSettings());
        }

Below is the error information.

Any help is appreciated.