One gotcha when importing configuration to a Drupal site can be a message that tells you that the configuration you are trying to import is from another site.
Here is the error that can be seen on the Configuration Synchronize page.
The staged configuration cannot be imported, because it originates from a different site than this site. You can only synchronize configuration between cloned instances of this site.
This error happens because the UUID of the site (in the database) is different to that in the configuration (in the code). The UUID in the code is stored in the configuration file system.site.yml. The reason for this check is to ensure that your don't destroy your Drupal site by installing configuration that was created from another site.