Reboot your Hypervisor and enter on BIOS, then, search for virtualization features or VT features and enable them.
Other way can be set virtual machine as 32bit computer: https://pubs.vmware.com/vsphere-50/topic/com.vmware.vsphere.vm_admin.doc_50/GUID-3B66132C-F3E7-4F86-836F-80A03AC99E2A.html
If you use NetScaler you will want to see these guides. The NetScaler How To Guides show administrators how to get NetScaler up and configured by providing instructions for common scenarios and some not so common ones.
This Micro Tutorial steps you through the configuration steps to configure your ESXi host Management Network settings and test the management network, ensure the host is recognized by the DNS Server, configure a new password, and the troubleshooting…