I had the exact same issue. I finally went back through all the instructions one by one and found that I missed a step. I don’t think it was called specifically in the plugin but after you follow the steps to “Becoming an Associate” you need to then follow the steps for “Becoming a Product Advertising API Developer”. (http://docs.aws.amazon.com/AWSECommerceService/latest/DG/becomingDev.html) After I followed these instructions I was given a new access id & key which I added to the plugin settings and everything worked! Good luck, I hope this helps anyone else having the same problem, and I really think Amazon should make these steps a little more clear and easy to understand.
Nevermind, I found it.
Line 48:
html{background-color:<?php echo $bodyclr; ?>;overflow:hidden;} <?php }
Removed overflow:hidden;
