Display error notice if EP is not install and active.

includes/Classifai/Admin/Settings.php

@@ -8,6 +8,7 @@
 use function Classifai\get_plugin;
 use function Classifai\get_services_menu;
 use function Classifai\get_post_statuses_for_language_settings;
+use function Classifai\is_elasticpress_installed;
 
 class Settings {
 
@@ -83,12 +84,13 @@ public function admin_enqueue_scripts( $hook_suffix ) {
 		wp_set_script_translations( 'classifai-settings', 'classifai' );
 
 		$data = array(
-			'features'     => $this->get_features(),
-			'services'     => get_services_menu(),
-			'settings'     => $this->get_settings(),
-			'dashboardUrl' => admin_url( '/' ),
-			'nonce'        => wp_create_nonce( 'classifai-previewer-action' ),
-			'postStatuses' => get_post_statuses_for_language_settings(),
+			'features'      => $this->get_features(),
+			'services'      => get_services_menu(),
+			'settings'      => $this->get_settings(),
+			'dashboardUrl'  => admin_url( '/' ),
+			'nonce'         => wp_create_nonce( 'classifai-previewer-action' ),
+			'postStatuses'  => get_post_statuses_for_language_settings(),
+			'isEPinstalled' => is_elasticpress_installed(),
 		);
 
 		wp_add_inline_script(

src/js/settings/components/feature-settings/index.js

@@ -51,6 +51,21 @@ const PersonalizerDeprecationNotice = () => (
 	</Notice>
 );
 
+const ElasticPressRequiredNotice = () => (
+	<Notice
+		status="error"
+		isDismissible={ false }
+		className="elasticpress-required-notice"
+	>
+		<p>
+			{ __(
+				'The Smart 404 Feature requires the ElasticPress plugin to be installed and active prior to use.',
+				'classifai'
+			) }
+		</p>
+	</Notice>
+);
+
 /**
  * Feature Settings component.
  *
@@ -83,6 +98,14 @@ export const FeatureSettings = ( { onSaveSuccess = () => {} } ) => {
 		);
 	}
 
+	// Show ElasticPress required notice if the feature is Smart 404 and ElasticPress is not active.
+	if (
+		'feature_smart_404' === featureName &&
+		! window.classifAISettings?.isEPinstalled
+	) {
+		return <ElasticPressRequiredNotice />;
+	}
+
 	return (
 		<>
 			{ 'feature_recommended_content' === featureName && (