The guest machine entered an invalid state while waiting for it to boot. Valid states are 'starting, running'

An error when I was installing Laravel 5.4 on an Ubuntu VM is below.

vagrant up
The guest machine entered an invalid state while waiting for it to boot. Valid states are 'starting, running'. The machine is in the 'paused' state. Please verify everything is configured properly and try again.

If the provider you're using has a GUI that comes with it, it is often helpful to open that and watch the machine, since the GUI often has more helpful error messages than Vagrant can retrieve.
For example, if you're using VirtualBox, run `vagrant up` while the VirtualBox GUI is open.

The primary issue for this error is that the provider you're using is not properly configured. This is very rarely a Vagrant issue.

The fix I found for this was loading the GUI in Virtual Box on vagrant reload by adding.

config.vm.provider "virtualbox" do |vb|
   vb.gui = true
end

to the end of my ~/Homestead/Vagrantfile and then running

vagrant reload

This loaded up the Virtual Box and an error appeared explaining I hadn't enabled Visualization on my VM. So closing the VM and enabling it then running it again fixed it.