[security_exception] authentication/authorization failure

I have a container deployed to AWS Kubernetes, when exists method gets called, I get this exception below. Any idea?

Error:

[security_exception] authentication/authorization failure
	at org.opensearch.client.transport.aws.AwsSdk2Transport.parseResponse(AwsSdk2Transport.java:541) ~[opensearch-java-2.22.0.jar!/:?]

Java code:

SdkHttpClient httpClient = ApacheHttpClient.builder().build();

OpenSearchClient client = new OpenSearchClient(
    new AwsSdk2Transport(
        httpClient,
        "search-...us-west-2.es.amazonaws.com", // OpenSearch endpoint, without https://
        "es",
        Region.US_WEST_2, // signing service region
        AwsSdk2TransportOptions.builder().build()
    )
);

String indexName = "test-index";

BooleanResponse booleanResponse = openSearchClient
                    .indices()
                    .exists(ExistsRequest.of(builder -> builder.index(List.of(indexName))));

Start at AwsSdk2Transport.java:541 and the indices().exists call shown in the report, then compare the AWS Kubernetes deployment's authentication and authorization setup with the client configuration. Reproduce the security_exception and identify the missing or incorrect configuration needed for the exists request to succeed.