Amazon S3 Batch Replication provides you a way to replicate objects that existed before a replication configuration was in place, objects that have previously been replicated, and objects that have failed replication. This is done through the use of a Batch Operations job.
You should note that batch replication differs from live replication which continuously and automatically replicates new objects across Amazon S3 buckets. You cannot directly use the AWS S3 console to configure cross-Region replication for existing objects. By default, replication only supports copying new Amazon S3 objects after it is enabled using the AWS S3 console. Replication enables automatic, asynchronous copying of objects across Amazon S3 buckets. Buckets that are configured for object replication can be owned by the same AWS account or by different accounts. Object may be replicated to a single destination bucket or multiple destination buckets. Destination buckets can be in different AWS Regions or within the same Region as the source bucket. Once done, you can delete the replication configuration, as it ensures that batch replication is only used for this one-time data copy operation.
If you want to enable live replication for existing objects for your bucket, you must contact AWS Support and raise a support ticket. This is required to ensure that replication is configured correctly