解决：Your VM has become "inaccessible."

Bringing machine 'homestead-7' up with 'virtualbox' provider...
==> homestead-7: Checking if box 'laravel/homestead' is up to date...
Your VM has become "inaccessible." Unfortunately, this is a critical error
with VirtualBox that Vagrant can not cleanly recover from. Please open VirtualBox
and clear out your inaccessible virtual machines or find a way to fix
them.

先进入到与之对应的目录：例如我的目录是（进入到红色字体的目录）

C:\Users\pc\VirtualBox VMs\homestead-7

在目录下看到有.vbox-tmp格式的文件，把-tmp删除。再次运行vagrant up看看是否能启动。