The VirtualBox VM was created with a user that doesn't match the current user running Vagrant.

Error Message

The VirtualBox VM was created with a user that doesn't match the
current user running Vagrant. VirtualBox requires that the same user
be used to manage the VM that was created. Please re-run Vagrant with
that user. This is not a Vagrant issue.

Cause

You copied someone vagrant box or your own from one machine to another. The box comes with its own settings that are specific to the user so they need to be removed.

Solution

Simply remove the .vagrant directory

$ rm -rf .vagrant