Your requirements could not be resolved to an installable set of packages. Problem 1 - Root composer.json requires acquia/acquia_cms * -> satisfiable by acquia/acquia_cms[dev-develop]. - acquia/acquia_cms dev-develop requires drush/drush ^10 || ^11 || ^12 -> found drush/drush[10.0.0-alpha1, ..., 10.x-dev, 11.0.0-rc1, ..., 11.x-dev, 12.0.0-beta1, ..., 12.x-dev] but it conflicts with your root composer.json require (13.1.1).