Vagrant/Homestead fails to boot unless VirtualBox UI open

I'm using a very straight forward Vagrant/Homestead setup. Brand new Windows 10 install and followed the documentation exactly.

When I run vagrant up, the virtual machine is created and begins to boot up but hangs on homestead: SSH auth method: private key and eventually fails. However, if I do the same thing but have the VirtualBox UI open, everything works normally and the VM boots up fine.

What's going on?