DevDesktop 2 (including the current release Sep 20, 2018 ) are designed to work with drush versions 8.x and the Acquia Cloud API v1.
While there are complete Acquia Hosting commands for Acquia Cloud API v1 for drush 8, the next major version of drush - drush 9 is a complete re-write of those shell commands.
We only have limited support for drush 9 commands in the current versions of Dev Desktop, and we recommend that if you prefer to use the DevDesktop environment, you modify your sites' composer.json file to use only drush 8.
this can be done with:
composer global require drush/drush:8.1.17
For more about using composer require to specify a version of drush see https://docs.drush.org/en/8.x/install-alternative/