How can I make my back4app app use a custom s3 bucket under my own aws account?

Question

I have set the following settings.

Environment variables:

AWS_ACCESS_KEY_ID={my access key name}
AWS_SECRET_ACCESS_KEY={my access key}

Custom Parse settings:

"filesAdapter": {
    "module": "@parse/s3-files-adapter",
    "options": {
        "bucket": {my bucket name},
        "region": "us-west-2"
    }
}

In AWS, I've created that bucket, created an IAM user with access to the bucket and the access key that I put into the environment variables.

Not sure why this isn't working. Is there anything else I should be doing? Thanks.