AWSFirehoseRecorder saveRecord seems never saving any record

In app didFinishLaunchingWithOptions

    let credentialProvider = AWSCognitoCredentialsProvider(regionType: .USEast1, identityPoolId: "my-identity-pool-id")
    let configuration = AWSServiceConfiguration(region: .USEast1, credentialsProvider: credentialProvider)
    AWSFirehoseRecorder.register(with: configuration!, forKey: "somestupidkey")

In view controller

let firehoseRecorder = AWSFirehoseRecorder(forKey: "somestupidkey")
let yourData = "Test_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_dataTest_data".data(using: .utf8)
firehoseRecorder.saveRecord(yourData, streamName: kinesisDirectory)

NSLog("Added %d records", firehoseRecorder.diskBytesUsed) // ALWAYS ZERO!!!!

It looks like it's not writing data at all. diskBytesUsed always returns 0. Any idea what might be issue?
Thanks

Ok, solved it. It turned to be authentication issue. So using this code will actually catch the error message of why the records weren't submitted:

            firehoseRecorder?.saveRecord(jsonData, streamName: "YourStreamName").continueOnSuccessWith(block: { (task:AWSTask) -> AWSTask? in
                NSLog("RecordBeen saved")
                return nil;
            }).continueWith(block: { (task:AWSTask) -> Any? in
                if let error = task.error as? NSError {
                    print("Error: \(error)")
                    return nil
                }
                return nil
            })

Showing error messages actually helped.

Hope it helps someone else having same issue.

Thanks.