The VirtualBox was created with a user that doesn't match the current user running Vagrant. VirtualBox requires 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.
Your UID: x
go to .vagrant/machines/web/virtualbox/creator_uid and set the value to your UID.
A VirtualBox machine with the name "name" already exists. Please use another name or delete the machine with the existing name, and try again.
vboxmanage list vms