Resolved once error.

js/inotify.js

-(function ($, Drupal) {
+(function ($, Drupal, once) {
   'use strict';
   Drupal.behaviors.inotify = {};
+  // Define the inotify behavior.
+  Drupal.behaviors.inotify = {
+    attach: function (context, settings) {
+      // Attach the NotificationsBlockEvents behavior.
+      once('inotify-opener-behaviors', '.inotify-opener', context).forEach(function (element) {
+        $('.inotify-block-content').toggleClass('active');
+        $('.inotify-opener .count.hidden').hide();
+      });
+
+      $('body').on('click', function (evt) {
+        if (!$(evt.target).closest('.inotify-block').length) {
+          if ($('.inotify-block-content').hasClass('active')) {
+            $('.inotify-block-content').toggleClass('active');
+          }
+        }
+      });
+    }
+  };
+
+  // Define the RefreshNotificationsView function.
   Drupal.behaviors.inotify.RefreshNotificationsView = function () {
     // Find the notification view.
     $.each(Drupal.views.instances, function getInstance(index, element) {
@@ -15,23 +35,4 @@
     });
   };
 
-  Drupal.behaviors.NotificationsBlockEvents = {
-    attach: function (context, settings) {
-      $('.inotify-opener').once().click(function () {
-        $('.inotify-block-content').toggleClass('active');
-        $('.inotify-opener .count').hide();
-      });
-      $('body').click(function (evt) {
-        if ($(evt.target).closest('.inotify-block').length) {
-          return;
-        }
-        else {
-          if ($('.inotify-block-content').hasClass('active')) {
-            $('.inotify-block-content').toggleClass('active')
-          }
-        }
-      });
-    }
-  };
-
-})(jQuery, Drupal);
+})(jQuery, Drupal, once);