HTTP Sink Connector Batching not working

I am using below HTTP Sink connector config and it is still sending records one by one. It is supposed to send data in a batch of 50 messages.

{
	"name": "HTTPSinkConnector_1",
	"config": {
		"topics": "topic_1",
		"tasks.max": "1",
		"connector.class": "io.confluent.connect.http.HttpSinkConnector",
		"http.api.url": "http://localhost/messageHandler",
		"request.method": "POST",
		"key.converter":"org.apache.kafka.connect.storage.StringConverter",
		"value.converter": "io.confluent.connect.avro.AvroConverter",
		"value.converter.schema.registry.url": "http://schema-registry:8081",
		"confluent.topic.bootstrap.servers": "kafka:19092",
		"confluent.topic.replication.factor": "1",
		"batching.enabled": true,
		"batch.max.size": 50,
		"reporter.bootstrap.servers": "kafka:19092",
		"reporter.result.topic.name": "success-responses",
		"reporter.result.topic.replication.factor": "1",
		"reporter.error.topic.name": "error-responses",
		"reporter.error.topic.replication.factor": "1",
		"request.body.format": "json"
	}
}

Could someone please suggest if any another property is missing.

Have you checked your message headers and their values? As per the docs:

The HTTP Sink connector does not batch requests for messages containing Kafka header values that are different.