When a Drupal site is installed, the UUID is set. This UUID is added to the exported configuration entities and is represented by the uuid key. Drupal uses this key to identify the source of the configuration. Drupal will not synchronize configurations that do not have a matching UUID in their YAML definition.

You can review the site's current UUID value by reviewing the system.site configuration object. This can also be done using the Drush or Drupal Console command-line tool.

Using Drush, type the following command:

$ drush config-get system.site

Using Drupal Console, type the following command:

$ drupal debug:config system.site