Product Advertising API (PA API) Error PA-API 5.0! HTTP Status Code: 401 Error

Greetings Community,

We are trying to hook up the Product Advertising API for the Amazon Associate program and we get the following error:

Error: Error calling PA-API 5.0! HTTP Status Code: 401 Error Type: UnrecognizedClient Error Message: The Access Key ID or security token included in the request is invalid.

Any idea on how to troubleshoot this issue? We have refreshed the keys 2x and tried to connect from two different Wordpress Websites.

Any help is appreciated!