When you receive an error code 0xC004C008 with the message as "The activation server reported that the product key has exceeded its unlock limit". This is an issue with the KMS key which has been activated for up to 10 times on six different computers. So if you need to activate your existing computer, you will need to contact the Microsoft Activation Call Center.

KMS stands for Key Management Services which is used by an enterprise to activate computers which go on and off the network. These computers need to connect at least once every 180 days.

The best part is KMS keys can be recycled so you can also connect with your Enterprise Admin to help you connect to the network, and get new KMS key to reactivate Windows Key.