What do you mean by "cannot enter Subscribe?"
Do you mean simply that you are unable to activate on either computer and the key is reported as being invalid?
If so, please try viewing the retail key (the one inside the case) with a magnifying glass as the characters can sometimes be hard to read.
You can contact support for help with this - via email. If you can provide a digital image (photo or scan) of the product key when support replies, they can advise the correct key.
How to reach support (FAQ) - http://forums.microsoft.com/WindowsOneCare/ShowPost.aspx?PostID=2421771&SiteID=2
If you have activated a subscription on the first PC, you need to use the same LiveID to activate on the second PC.
-steve