Cant use AWS RDS Native Backup on MSSQL Database

Question

I'm moving resources from one AWS account to another and I need to move a database - the native database backup doesn't seems to work.

I configured the IAM Role and the RDS database has the native-backup feature in the option groups.

This is the error I'm getting after running rds_backup_database in the database:

Aborted the task because of a task failure or an overlap with your preferred backup window 
for RDS automated backup.
The S3 bucket location: us-east-1 does not match the RDS instance region: us-west-2. 
Please specify a bucket that is in the same region as RDS instance.

Pretty obvious, huh?

The thing is that I specifically created the S3 Bucket in the region us-west-2 (or Oregon) but the error stays the same.

I even have created a couple more buckets in others regions, but the error stays the same (with the same bucket region).

The last thing I tried was to edit the policy and give the most permissive that I could:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": "s3:*",
      "Resource": "*"
    }
  ]
}

Any ideas?