If this was a previously added target, make sure you first remove it before trying to add it back.
Its possible the target's or the server's key was changed in the upgrade process, which can result in the target or server rejecting one another. To double check if this was the case you can use an SSH client like Putty to connect to the target and run more /var/log/salt/minion to check the log. If the target is rejected its salt-minion process will stop. To restart the salt-minion process you can reboot the target or run /etc/init.d/salt-minion start
From the server you can also run cmd as an administrator and then navigate to c:\Program Files\National Instruments\Shared\salt and run salt-key to see the salt key approval status for all of the minions. If something is denied it most likely tried to connect using using the same minion ID as before, but with a different key. You can then run salt-key -d <minion ID> to clean it up and then try adding the target again.
