When you get this error, it generally means that your Authorize.NET settings and the settings in your LinkU control panel do not match.

To correct the error, try re-entering your Authorize.net API login ID and Transaction key into your LinkU settings. Be sure each setting is in the correct field. For example, if you placed the API login ID information in the Transaction Key field and vice versa.

Sometimes this happens if you change the settings or request a new transaction key in Authorize.NET. When you do this, the old one stops working and users will get this error when attempting to checkout on the website.