There were errors validating the config synchronization

Drupal\Core\Config\ConfigImporterException: There were errors validating the config synchronization. [error] Entities exist of type Custom block and Custom block type ADV. These entities need to be deleted before importing. in Drupal\Core\Config\ConfigImporter->validate() (line 750 of /var/www/html/web/core/lib/Drupal/Core/Config/ConfigImporter.php). The import failed due for the following reasons: [error] Entities exist of type Custom block and Custom block type ADV. These entities need to be deleted before importing.