Our apologies that you are encountering this issue. The problem you are facing is due to the Autodesk single sign on that is needed when you have multiple Autodesk products. My guess is that you likely have AutoCAD installed on this mac as well. While we are working on a multi-product solution, here is a link to a workaround that should get you productive.
The workaround involves clearing your AdSSo file but please note that there are 2 locations that could confuse you. We need you to go to the SYSTEM – Library and NOT the users-library. Once this file is deleted it needs to be removed from the trash can as well. Once again, not the users -library but the system library – the link has details.
Phil Eichmiller
Software Engineer
Quality Assurance
Autodesk, Inc.