Had the same problem once i updated windows. Online i found this...
"If your unRAID folders are public, use 'guest' as username and '1234' as the password and tick the 'remember my credentials'"
However, What i did that worked for me was just enter the name of my server (Tower) as the user, and my root user password as the password which worked. Then just click "remember my credentials" so you dont have to do it again every restart.