Why is my API key not working?
API keys have multiple dependencies that can result in errors like: "The user is not authorized for this operation based on …". Please make sure you are using the correct credentials and endpoint with the correct API key. For example, your production API key is only able to make calls to the API production endpoint. The keys are also often linked to your specific customer credentials such as customer number and customer code - please make sure to use the credentials PostNL has provided for implementation.