Vagrantにて、SSH auth method: private keyで止まってしまう

使用環境: Windows10

vagrant init
# ここでVagrantfile編集
vagrant up

としたのですが、

Bringing machine 'default' up with 'virtualbox' provider...
==> default: Importing base box 'bento/centos-7.2'...
==> default: Matching MAC address for NAT networking...
==> default: Checking if box 'bento/centos-7.2' version '2.3.1' is up to date...
==> default: Setting the name of the VM: ubuntu18_default_1556849833645_39945
==> default: Clearing any previously set network interfaces...
==> default: Preparing network interfaces based on configuration...
    default: Adapter 1: nat
==> default: Forwarding ports...
    default: 22 (guest) => 2222 (host) (adapter 1)
==> default: Running 'pre-boot' VM customizations...
==> default: Booting VM...
==> default: Waiting for machine to boot. This may take a few minutes...
    default: SSH address: 127.0.0.1:2222
    default: SSH username: vagrant
    default: SSH auth method: private key
Timed out while waiting for the machine to boot. This means that
Vagrant was unable to communicate with the guest machine within
the configured ("config.vm.boot_timeout" value) time period.

If you look above, you should be able to see the error(s) that
Vagrant had when attempting to connect to the machine. These errors
are usually good hints as to what may be wrong.

If you're using a custom box, make sure that networking is properly
working and you're able to connect to the machine. It is a common
problem that networking isn't setup properly in these boxes.
Verify that authentication configurations are also setup properly,
as well.

If the box appears to be booting properly, you may want to increase
the timeout ("config.vm.boot_timeout") value.

というエラーが出てしまいます。

vagrant sshもできないので、Vagrantにおける鍵の設定の話も調べたのですが、.vagrant\machines\default\virtualbox\private_keyがそもそも見当たらず、困っています。

Vagrantfileは以下の通りです

ruby
1# -*- mode: ruby -*-
2# vi: set ft=ruby :
3
4# 設定バージョン
5Vagrant.configure("2") do |config|
6
7  # 起動ボックスの指定
8  config.vm.box = "bento/centos-7.2"
9  # デバッグ用に起動タイムアウトを短くしておく設定
10  config.vm.boot_timeout = 60
11
12  config.ssh.insert_key = true
13
14  config.vm.provider "virtualbox" do |vb|
15    vb.gui = true
16    vb.memory = "1024"
17    # VMのケーブルの設定
18    vb.customize ['modifyvm', :id, '--cableconnected1', 'on']
19  end
20end
21