In the case of you get error: "VT-x/AMD-V hardware acceleration is not available on your system" when running a 64 bit virtual device, the following steps can help you solve this problem:
1. Your CPU (Intel/AMD) must support 64 bit with virtualization technologies. You must enable it in the BIOS setting. To know where, let dig on searching your BIOS manual. For example in the BIOS of my PC, it is in Configuration menu:
2. If you are using Windows 7/8/10, let turn off Hyper-V feature:
3. Restart your PC, open Genymotion and download your favorite 64 bit virtual device for using.