...
A: HyperV or Docker have been installed, and are interfering with the nested virtualization process. For Docker, try uninstalling.
For HyperV, open and an admin command prompt and enter either "dism.exe /Online /Disable-Feature:Microsoft-Hyper-V" or "dism.exe /Online /Disable-Feature:HypervisorPlatform". The difference depends on what build of WIndows 10 is running.
...