I would like to know why if I already made the steps to import emails in my Amazon account, it appears to me that you are having problems to connect with my account ???
Try to check Amazon Seller Central and check if Feedbackz is listed and click on "Confirm Access"
Also, try to review the details entered make sure there is no extra space before or after each credential or any missing character from here: https://app.feedbackz.com/companies
Sometimes the Marketplace ID may be entered instead of Seller ID, so that can also cause an error. You may want to try the steps again in Syncing your Amazon account.