Why does rds_tlog_backup_copy_to_S3 result in an internal error in processing the task

I've got a RDS MSSQL 2014 running. I can create backups on an S3. I was trying to start log-shipping for replication.

Followed the documentation https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/USER.SQLServer.AddlFeat.TransactionLogAccess.html

I've setup the bucket, with the policy and owner rights. I've executed the setup sp as well. Worked fine. msdb.dbo.rds_tlog_copy_setup

However, when I execute rds_tlog_backup_copy_to_S3. the task that gets created results in an error with the following message:

[2023-04-06 06:47:22.123] Task execution has started. >

[2023-04-06 06:47:22.303] Task has been aborted

[2023-04-06 06:47:22.307] There was an internal error in processing the task. Try again at a later time.

I've ensured that my KMS keys used in rds_tlog_copy_setup is the same as the one used for RDS