Earlier today I got this error
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.
I think this happened because I deleted the directory where virtual box store info. about the VM. Since virtual box could not access these VM metadata, vagrant could not also.
Anyway, I resolved the issue by deleting the .vagrant file created by vagrant and did a
vagrant up
If you have multiple vagrant VMs running on the same machine, you run he following scripts.
find path/to/vagrant/vm -n ".vagrant" | xargs rm