The KMS host that is used is very probably a Windows Server 2008 KMS host that cannot standard activate Windows 7 and 2008 R2 machines.
When you do not have Windows Server 2008 R2 KMS host key have then you must have a Volume License agreement so that your request your Windows 7 and Windows 2008 R2 kms keys.
-If the KMS host a Windows Server 2003 SP2 machine is you have the update from the KB article KB968915 install and restart the machine.
-If the KMS host a Windows Server 2008 SP2 machine is you have the update from the KB article KB968912 install and start the new machine.
-If the KMS host one Windows Server 2008 R2 machine is you have to install any further update.
You the new KMS host key import now. The commands are as follows:
1. Uninstall KMS license Key on host – slmgr.vbs /upk
2. Install Windows Server 2008 R2 KMS license key – slmgr.vbs /ipk <Your Key>
3. Activate KMS server online: slmgr.vbs /ato
4. Net Stop slsvc
5. Net Start slsvc
The clients can now activate