There is no password for the user. The service is using your key to authenticate.

You need to make sure the role you are using has the trust relationship. It should look like:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": [
          "transfer.amazonaws.com"
        ]
      },
      "Action": "sts:AssumeRole"
    }
  ]
}

There is no password for the user. The service is using your key to authenticate.

You need to make sure the role you are using has the trust relationship to transfer.amazonaws.com. It should look like:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Principal": {
        "Service": [
          "transfer.amazonaws.com"
        ]
      },
      "Action": "sts:AssumeRole"
    }
  ]
}