You may run "slmgr /upk [Activation ID]" or "slmgr /ckms [Activation ID]" (without quotes) command with high priviledge.
Here is a related article can be referred to.
TechNet Community Support
Do not run slmgr /UPK !
That removes all product keys from the system, leaving the machine in an unlicensed, unsupported state, some functionality will be broken without a product key on the system and there may be situations which you will not be able to recover from.
Slmgr /rearm resets the activation status, which is what should be used
Thanks, Darrell Gorter [MSFT] This posting is provided "AS IS" with no warranties, and confers no rights. VAMT - Volume Activation Management Tool - Download link http://www.microsoft.com/downloads/details.aspx?FamilyID=ec7156d2-2864-49ee-bfcb-777b898ad582&displaylang=en