Fatal error: Uncaught Error: Interface "Dhii\Validation\ValidatorInterface" not found in /var/www/html1/wp-content/plugins/zettle-pos-integration/src/Validation/RequiredPluginsValidator.php:16 Stack trace: #0 {main} thrown in /var/www/html1/wp-content/plugins/zettle-pos-integration/src/Validation/RequiredPluginsValidator.php on line 16