You can create Guest profile for Windows server 2016 with MAK key.
However, if the MAK key is not a multiple activation key, such as only supporting activation once, then, you may deploy the first VM from template successfully, but may experience with errors during deploying the second VM.
I would recommend to leave the product key as blank in Guest profile, and enter the product key in the Windows system after the VM is deployed.
Please remember to mark the replies as answers if they help.
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