Amazon requires that you acquire your AWS key by following the steps below. You can not just use an AWS key you use for S3 storage etc.

Amazon Setup

The Amazon key setup for new Amazon Associates has three parts: Associate Registration, API Registration and AWS key generation. It is important to do the steps in order.

1) Associate signup:

2) Api signup & AWS keys:

After signing up as an Associate you need to get api access.

http://docs.aws.amazon.com/AWSECommerceService/latest/DG/becomingDev.html

3)  Generate Keys

Sign in your Amazon account you just made. Use the same email address and password.

Go to Manage your account and then to the steps below:

  1. Sign in your AWS account at AWS Security Credentials Console. Use the same email address and password.
  2. A pop-up message appears. Click Continue to Security Credentials.
  3. Click Access Keys (Access Key ID and Secret Key).
  4. Click Create New Access Key, and then click Show Access Key or Download Key File to retrieve the credentials.
  5. Save the access key information in a safe location. You will use these credentials to make calls to the Product Advertising API.