SunFrog Shirts API

I am using SunFrog Shirts API. http://ift.tt/1IvYImO

API:: http://ift.tt/1AQO6IS

Request::

POST Form Fields
iAgree = 1
name = "Required"
email = "Required valid email"
password = "Required"
company = "Required"
address = "Required"
city = "Required"
state = "Required"
zipcode = "Required"
country = "Required". If USA, spell out entire country name, e.g. "United States".

But I am getting Failure response::

[
    {
        "ResponseAck": "Failure",
        "Message": "API Authentication Failure",
        "MessageDeveloper": "API Authentication Failure. Number or key is invalid."
    }
]