When you attempt to add or connect an ESXi host to vCenter Server, the operation might be unsuccessful.

You cannot add or connect an ESXi host to vCenter Server, and you receive one of the following error messages.

Cannot complete the operation. The vRAM limit of 192GB will be exceeded. Upgrade the vCenter Server license or decrease the amount of the consumed vRAM.
The host is licensed with VMware vSphere 5 Essentials. The license edition of vCenter Server does not support VMware vSphere 5 Essentials.

The host that you try to add or connect is licensed with vSphere 5.x Essentials that is part of the Essentials kits. You cannot use more than 192GB of pooled vRAM for hosts that are licensed with vSphere 5.х Essentials. The memory that is configured to the powered on virtual machines on the host that you try to add or connect will lead to exceeding 192GB of consumed vRAM. For details about vRAM and vRAM pooling, see License Management and Reporting from vCenter Server and Host Management.

Hosts that are licensed with vSphere 5.х Essentials can only be managed by vCenter Server systems that are licensed with vCenter Server 5.х Essentials. For example, if you try to add a host that is licensed with vSphere 5.х Essentials to a vCenter Server system that is licensed with vCenter Server 5.х Standard, the operation fails. vCenter Server 5.х Standard does not support vSphere 5.х Essentials.

Reduce the amount of memory that is configured for the powered-on virtual machines and retry to add or connect the ESXi host to vCenter Server.