亚马逊AWS访问Feeds.SubmitFeed被拒绝

我的API请求是这样的（摘录）：

   [method] => POST
    [uri] => Array
        (
            [scheme] => https
            [host] => mws.amazonservices.com
            [port] => 443
            [user] => 
            [pass] => 
            [path] => /
            [query] => Array
                (
                    [AWSAccessKeyId] => xxx
                    [Action] => SubmitFeed
                    [FeedType] => _POST_FLAT_FILE_FULFILLMENT_DATA_
                    [Marketplace] => xxx
                    [Merchant] => xxx
                    [SignatureMethod] => HmacSHA256
                    [SignatureVersion] => 2
                    [Timestamp] => 2012-04-04T11:42:54Z
                    [Version] => 2009-01-01
                    [Signature] => xxx=
                )

如果我在那里输入了相同的数据，我得到的响应也是一样的。

Array
(
    [ErrorResponse] => Array
        (
            [xmlns] => http://mws.amazonaws.com/doc/2009-01-01/
            [Error] => Array
                (
                    [Type] => Sender
                    [Code] => AccessDenied
                    [Message] => Access to Feeds.SubmitFeed is denied
                )
            [RequestID] => bac7376f-1b2b-41ae-b2d2-de974b217ee7
        )
)

除了API响应中的错误，当我尝试访问此URL时，我会得到"用户权限不足"https://sellercentral.amazon.com/gp/mws/registration/register.html具有讽刺意味的是，在我使用了联系表格后，亚马逊告诉我要注册的URL…

为什么会出现此错误？我错过了什么？在这成千上万的页面和注册的混乱中，我在哪里忘记了注册或同意什么？