Hello,
Read the answer from the plugin author https://codecanyon.net/item/woocommerce-amazon-affiliates-wordpress-plugin/3057503/comments?page=344&filter=all#comment_24595952
It seems the api keys that you’re using are not valid. Please test them on scratchpad: https://webservices.amazon.com/paapi5/scratchpad/index.html
Read the WooZone docs about the API key http://docs.aa-team.com/woocommerce-amazon-affiliates/documentation/wzone-pa-api-5/ https://youtu.be/KMfz_Auazuc
Regards
