If you received this message, it means that the extension was unable to retrieve an xml file with the data. Please check if you have entered the correct The Feedback Company ID. Please note that The Feedback Company uses two different IDs.
Find the correct code:
Login to https://beheer.feedbackcompany.nl and navigate to "My Account" (Mijn Account). Here, you will find the field: "The Feedback Company ID". Copy and paste this number to the field in your Magento Admin.