The issue is the customer is getting an error message "Invalid Assignment" when trying to attempt to connect NAV to Avatax?
The environment is Microsoft Dynamics NAV 2009 R2
The resolution is to ensure that the customer enters the correct Customer ID, Account Key and URL to ensure a successful verification of the connection to the admin console.
The cause is customer keyed in incorrect information when trying to enter information into the Avatax Configuration page.
Note: AvaTax for Microsoft Dynamics NAV 2009 is sunsetted and no longer supported by Avalara as of April 30, 2016. This existing knowledge base documentation is available to provide known paths to resolution for documented issues. If you are using a version affected by service discontinuation and want to maintain access to Avalara Support, you’ll need to upgrade to the latest version of the integration as soon as possible