I've been trying for the life of me to install macOS Sierra 10.12.3 in a Parallels VM. I somehow got a clean install to work before, but not since. It loads up the Install macOS Sierra.app just fine, I get to the recovery window page, click Install a new copy of macOS Sierra, click continue and it just sits there with the continue button greyed out. all the other functions of the recovery window work fine but not the installation portion. I've tried this with a brand new installer from the Mac App Store, from a bootable USB Drive, 10.12.0, 10.12.1, 10.12.2, etc For this VM instance upgrading from El Cap to Sierra is not a solution, I need to perform a clean install of Sierra.