How to use hardware virtualization?

I have used hardware assisted virtualization in over a year now. The difference in performance is huge. But last week is stop working. This is critical as I spend most of my workday in VmWare Workstation.

I got a message

VMware Workstation does not support nested virtualization on this host. Module 'MonitorMode' power on failed. Failed to start the virtual machine.

If I uncheck checkbox Settings/Processors/Virtualize Intel VT-x/EPT or AMD-V/RVI the VM starts fine but with slower performance.

So something must have changed! I suspect a Windows update.

Version: VmWare WorkStation Pro 15.5.7 Build-17171714

Host: Windows 10 Enterprise 20H2 64-bit

Guest: Windows 10 Pro 20H2 64-bit

CPU is Intel Core I7 9th generation with 32 GB RAM.

What are my options ?

• First I try to contact VmWare support. But it was incredible complicated, Maybe I have to buy support ?
• Upgrade to latest VmWare 16.1 ? I can do that if I am sure it helps.
• I suspect Hyper-V is still active and cause a conflict with VmWare hypervisor. But how do I turn off Hyper-V apart from the obvious in "Turn Windows features off and on" ?

I asked the same question in VmWare forum without response. I really need a fix for this!

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