As of Drupal 8, configuration can be migrated between servers. Enabled languages are configuration, but the translations themselves are NOT configuration. When the configuration for a new language is pushed to a new server, the language is enabled, but there is no way to force Drupal to re-download the translations from the remote server.

This module creates a new Drush command, locale:rebuild that wipes all the translations from the system, and re-imports them from the Drupal language server.

Usage: