You attempt to activate a new Windows Server 2012 R2 KMS server as an Active Directory-Based Activation:
… but receive the following error:
The following error has occurred. Please resolve the error and try again.
Access is denied.
The reason this error is presented is because the KMS server is not a domain controller. The following TechNet article describes the requirements for setting up an an Active Directory-Based Activation KMS server:
Activate using Active Directory-based activation