I am also facing same problem. It seem issue from apple server.

Today, I am facing same problem. Hope apple will resolve soon. I think we should wait and don't modify our configuration.

@hejun it doesn't works for me.

Once succeed and then failed again with another issue

Ooh no i got another issue We've received too many API requests for this API key in the past 60 seconds. Please wait and tr again. With error code RATE LIMIT EXCEEDED for id (null)

Finallyyyy.... Today morning successfully uploaded to appstore.