diff --git a/mailchimp.services.yml b/mailchimp.services.yml
index e5be4fc..01be062 100644
--- a/mailchimp.services.yml
+++ b/mailchimp.services.yml
@@ -25,4 +25,4 @@ services:
 
   mailchimp.client_factory:
     class: Drupal\mailchimp\ClientFactory
-    arguments: ['@mailchimp.settings', '@logger.channel.mailchimp']
+    arguments: ['@mailchimp.settings', '@logger.channel.mailchimp', '@messenger']
diff --git a/src/ClientFactory.php b/src/ClientFactory.php
index 7975ce2..dfb70ef 100644
--- a/src/ClientFactory.php
+++ b/src/ClientFactory.php
@@ -3,9 +3,10 @@
 namespace Drupal\mailchimp;
 
 use Drupal\Core\Config\Config;
-use Drupal\mailchimp\Exception\ClientFactoryException;
+use Drupal\Core\Messenger\MessengerInterface;
 use Mailchimp\Mailchimp;
 use Psr\Log\LoggerInterface;
+use Drupal\mailchimp\Exception\ClientFactoryException;
 
 /**
  * Factory for Mailchimp PHP Library.
@@ -17,14 +18,21 @@ class ClientFactory {
    *
    * @var \Drupal\Core\Config\Config
    */
-  protected $config;
+  protected Config $config;
 
   /**
    * Mailchimp logging interface.
    *
    * @var \Psr\Log\LoggerInterface
    */
-  protected $logger;
+  protected LoggerInterface $logger;
+
+  /**
+   * Messenger Service.
+   *
+   * @var \Drupal\Core\Messenger\MessengerInterface
+   */
+  protected MessengerInterface $messenger;
 
   /**
    * Mailchimp Library instances, keyed by class name.
@@ -40,10 +48,13 @@ class ClientFactory {
    *   Mailchimp Settings.
    * @param \Psr\Log\LoggerInterface $logger
    *   Logging interface.
+   * @param \Drupal\Core\Messenger\MessengerInterface $messenger
+   *   Messenger Service.
    */
-  public function __construct(Config $config, LoggerInterface $logger) {
+  public function __construct(Config $config, LoggerInterface $logger, MessengerInterface $messenger) {
     $this->config = $config;
     $this->logger = $logger;
+    $this->messenger = $messenger;
   }
 
   /**
@@ -113,6 +124,7 @@ class ClientFactory {
     $api_key = $this->config->get('api_key');
     if (!strlen($api_key)) {
       $this->logger->error('Mailchimp API Key cannot be blank.');
+      $this->messenger->addError(t('Mailchimp API Key is needed for functionality to work.'));
       throw new ClientFactoryException('Mailchimp API Key cannot be blank');
     }