Drush not "seeing" Drupal installation
Try running drush from inside the VM.

First, use vagrant ssh to get inside.

Then, change directory to the docroot:

cd /vagrant/docroot/

You should be able to run Drush commands from there.

In theory, if you know how to set up Drush aliases, you won't need to do that, but this method is a useful shortcut.

Let me know if it works -- and good luck!