wrong product key error

I am trying to install product key for computers 1-11 and the product key worked for computer 1 but will not work for additional computers.  I purchased keys for 11 computers and was sent one. Please advise.

If you have an OS image that you are using to create new setups, please follow the instructions provided in the Administrators Guide which is included with the installation of Secure Lockdown.

I am typing it in and am no mistyping the key.

Currently, you have 10 licenses remaining, so you must not be entering the key properly. Please try cutting and pasting it from the email that was sent to you containing the product activation (license) key.