I install the Windows 10 May 2019 Update and attempted to install Sandbox mode.
When I went to install the feature the “Window Sandbox” option was disabled with a tool tip that said, “Virtualization support is disabled in the firmware”. Hyper-V HyperVisor and Windows Defender Application Guard were also disabled.
I couldn’t find any clear instructions except to play with setting in the BIOS until it works. So that is what I did.
I am using a Gigabyte X470 Aorus Ultra Gaming motherboard, but this may be applicable to many others (or not).
After looking up each BIOS setting I discovered the issue was SVM Mode was disabled. This is apparently the AMD Secure Virtual Mode. Enabling it allows me to install all the virtual machine features.
For the my mother board it was hard to find. In the BIOS I went to M.I.T category, then Advanced Frequency Settings->Advanced CPU Core Settings and then you will find SVN Mode.