Amazon Checkout Malfunctioning

I implemented Amazon Checkout:

I have correct permissions for all files/directories

I am in the production mode at amazon's site

I have triple checked Merchant ID, Access Key ID & Secret Access Key and set the correct callback URL.

P.S> what is CS-Cart talking about when it asks for “Public Key”? There seems to be no such thing, my best guess was Amazon refers to this as the “Access Key ID”.

After all this I get the following error (signature xx'd out) when trying to checkout on the storefront:

The order could not be authenticated. Detail: Your signature [xx] does not match the signature that we expect.

Hello SleeK,

The problem requires the investigation on your server. Please contact us via Customer Help Desk and provide us with a temporary access to your server.

As regards the “AWS access public key” setting, your AWS (Amazon Web Services) public key should be specified in this text input field.

Pavel Zyukin

CS-Cart Support team