If you are getting that message then it means you are on the registration page.  You will want to use the login page here:

http://www.wpmarketertools.com/login/

If you are already logged into your account, you can go directly to the members area here:

https://www.wpmarketertools.com/members/

If you are getting that message then it means you are not logged in to your account.  You will want to use the login page here:

http://www.wpmarketertools.com/login/

Please view the video below:

You can reset your password here:

https://www.wpmarketertools.com/wp-login.php?action=lostpassword

If you are not getting any results then there is an issue with the Amazon API Keys you entered.  Two things that you will want to check:

1.  Double check to make sure there is no spaces before or after your API Keys (which is the most common issue).

2.  Make sure you are signed up for the Product Advertising API.  You can register at: https://affiliate-program.amazon.com/gp/flex/advertising/api/sign-in.html.

If neither of those fixes the issue then you may need to create a fresh set of keys and use those new keys.

The first thing you will want to do is to deactivate all your other plugins and then see if that corrected the issue.  At that point you can start reactivating the other plugins and see which one is causing the issue.