Under certain conditions, you might not be able to assign a license key to an ESXi host asset.
You try to assign a license key to an ESXi host, but you cannot perform the operation and you receive an error message.
You might be unable to assign a license key to an ESXi host because of the following reasons:
The calculated license usage for the host exceeds the license capacity. For example, you have a vSphere Essentials license key with capacity for two processors. You try to assign the key to a host that has four processors. You cannot assign the key, because the required license usage for the host is four processors.
The features on the host do not match the license edition. For example, you might configure vMotion and DRS on a cluster of hosts while you are using evaluation mode. Later, you try to assign Standard license keys to the hosts. This operation fails because the Standard edition does not include vMotion and DRS.
You do not apply the correct license key.
The host is connected to a vCenter Server system that is assigned a license key that restricts the edition of the license that you want to assign. For example, vCenter Server is licensed with vCenter Server Standard, and the license key is for vSphere Essentials.
Assign a license key with larger capacity.
Upgrade the license edition to match the resources and features on the host, or disable the features and resources that do not match the license edition.
Assign a correct license key. To license ESXi hosts, you must assign a vSphere license key.
Assign a license key whose edition is compatible with the license edition of vCenter Server. For example, if vCenter Server is licensed with vCenter Server Standard, you need a vSphere Standard license key.