If you have a valid proof of purchase but cannot find the key, you can contact Microsoft Volume Licensing Support for assistance. Already Installed?

In some Volume License (VL) installers, the product key is "pre-keyed" and embedded in the setup files. You can find this manually by extracting the installer and checking the \server\amd64\license.txt file. Installation and Key Management

This guide provides the official 90-day trial product keys for Microsoft Dynamics CRM 2016 and outlines the key steps for installation and licensing. 90-Day Trial Product Keys

A common mistake is thinking the product key alone gives you full legal rights. It does not. The activates the server software, but to use it, each user or device requires a Client Access License (CAL) .