I have VAMT 2.0 installed on 2012 servers.  Works like a charm for my win 7 and Office 2010 MAK and KMS licenses.  Tried to add my 8.1 and office 2013 licenses and am being told the letter N is an illegal character and that my MAK licenses can not be verified and I may need to upgrade to 3.1.

Do I need to uninstall 2.0 before I update?

Hello,

You need the new version of the ADK which contains the updated VAMT, use the link below as the source to get the new version.

http://www.microsoft.com/en-US/download/details.aspx?id=39982

Hi dpuckhaber,

You may need to export/save the current data as .CIL files from the VAMT2.0 and then import it to the VAMT 3.1 database.
Here is a link for reference:
Upgrade VAMT 2.0 to VAMT 3.0 on same Windows 2008 R2 Server
https://social.technet.microsoft.com/Forums/windowsserver/en-US/4c4b3ef2-a497-4c3e-9888-8b8578d5fc45/upgrade-vamt-20-to-vamt-30-on-same-windows-2008-r2-server?forum=winservergen

Here is another discussion including the details of the whole process and it has been proved to work well.

Setup/migrate to VAMT 3.0
https://social.technet.microsoft.com/Forums/windows/en-US/e5bd06f0-d1a0-464d-9a0a-7c8384f07753/setupmigrate-to-vamt-30?forum=w8itproinstall

Best regrads