I need yields for govt issued 10 year bonds I am using the following request body which returns empty data.

 {
    "ExtractionRequest": {
        "@odata.type": "#ThomsonReuters.Dss.Api.Extractions.ExtractionRequests.ElektronTimeseriesExtractionRequest",
        "ContentFieldNames": [
            "Yield"
        ],
        "IdentifierList": {
            "@odata.type": "#ThomsonReuters.Dss.Api.Extractions.ExtractionRequests.InstrumentIdentifierList",
            "InstrumentIdentifiers": [
                {
                    "Identifier": "GB10YT=RR",
                    "IdentifierType": "Ric"
                }
            ],
            "UseUserPreferencesForValidationOptions": false
        },
        "Condition": {
            "ReportDateRangeType": "Range",
            "QueryStartDate": "2018-01-01T00:00:00.000Z",
            "QueryEndDate": "2018-02-01T00:00:00.000Z",
            "LastEntityOnly": false
        }
    }
}