You need at least vSphere 5.5 for the windowsHyperVGuest guest OS identifier. The blog post https://www.derekseaman.com/2014/06/nesting-hyper-v-2012-r2-esxi-5-5.html gives some tips for running nested Hyper-V. Hopefully, you can it working with these tips.
Thanks for your help. The version of vSphere is 6.0. I still got the error after trying these tips in the blog.
Assuming your processor is Intel, does it support Extended Page Tables (EPT)? Not all Intel processors support EPT even though they support Intel VT-x such as the older Xeons or some of the pre-Skylake unlocked K processors.
Thanks for your help. The processor type is Intel Xeon E3-1290 v2. and it supports EPT.
I suppose you must have seen this, too.
It mentions a checkbox "Expose hardware-assisted virtualization to the guest operating system." for the processor settings.
This might be the GUI equivalent of the vhv.enabled = "TRUE" in the vmx.
Depending on the editor you use to add the lines in the vmx, the double quotes sometimes becomes a problem especially if you copy and paste from the webpage; and it basically makes the parameters add in the vmx to be ignored.