On my Ubuntu 18.04, I\'ve installed VirtualBox 6.0 in order to have nested virtualization. Virtualization is
In Windows, go to VirtualBox installation folders -> type cmd on the bar (it will pop up cmd in that folder) -> type VBoxManage modifyvm YourVirtualBoxName --nested-hw-virt on -> enter.
VBoxManage modifyvm YourVirtualBoxName --nested-hw-virt on
Now it should been ticked.