Secrets Manager lambda call get_secret_value couldn't connect to endpoint URL

Endpointconnectionerror while retrieving secret using Lambda function.

When tried to access using the endpoint URL directly via web browser, got "<UnknownOperationException/>" (https://docs.aws.amazon.com/general/latest/gr/asm.html)

Checked AWS service health dashboard - no services are down as of now.

See the code below: client = session.client(service_name = "secretsmanager", region_name = region_name) get_secret_value_response = client.get_secret_value(SecretId = secret_name)