A hopefully quick question - I have just purchased Windows Server 2019 Essentials and installed it on three VM's no problems, however on the fourth one it won't activate and it says its because I have already used the product key before. This is all on the same hardware appliance and my understanding was that this was permitted so long as all the servers had the same physical CPU (ie. The Single CPU that is licensed) - Is that the correct understanding or am I missing something here.
Essentials edition allows to run one instance of the server software in one physical operating system environment, and one instance in one virtual operating system environment on the licensed server. If you run both permitted instances at the same time, the instance of the server software running in the physical operating system environment may be used only to run hardware virtualization software or provide hardware virtualization services.
Sounds like you'll need to license Standard edition twice or use a DataCenter edition license for this host.