Norton can't see my new computer

Next month I need to renew my subscription.  I have had Norton 360 for multiple computers but I don't need that anymore since I have only one desktop computer now.  When I go to my account, Norton shows that I have two devices each running Windows 7.  I have one device running Windows 10.  How do I get Norton to see my computer when I renew next month?  It hardly seems useful to update to two computers that don't exist anymore.