错误信息指出Amazon SP-API 的 getOrder API 不允许Root账户进行操作。要解决此问题，需要创建新的IAM用户来代替Root账户。并确保为该用户分配了必要的订单API权限。

以下是创建IAM用户，并在AWS控制台中为它分配订单API权限的代码示例：

import boto3

# 创建IAM User并获取User的Access Key ID和Secret Access Key
client = boto3.client('iam')
response = client.create_user(UserName='NewUser')
response = client.create_access_key(UserName='NewUser')
access_key_id = response['AccessKey']['AccessKeyId']
secret_access_key = response['AccessKey']['SecretAccessKey']

# 为User分配必要的API权限
policy = {
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "orders:ListOrders",
        "orders:GetOrder"
      ],
      "Resource": "*"
    }
  ]
}
client = boto3.client('iam')
response = client.create_policy(
  PolicyName='NewPolicy',
  PolicyDocument=json.dumps(policy)
)
policy_arn = response['Policy']['Arn']
response = client.attach_user_policy(
  UserName='NewUser',
  PolicyArn=policy_arn
)

这段代码会创建一个新的IAM User和一个新的Policy，然后将用于的API权限附加给User。使用新的Access Key ID和Secret Access Key来调用Amazon SP-API的getOrder API就可以成功执行操作了。