File: /var/www/html/wp-content/plugins/mailjet-for-wordpress/src/widget/views/designforfailure.php
<p>
<?php
if ($validApiCredentials == false) {
_e('Please make sure that you are using the correct API key and Secret key associated to your Mailjet account: <a href="https://app.mailjet.com/account/api_keys" target="_blank">https://app.mailjet.com/account/api_keys</a>', 'mailjet-for-wordpress');
} else {
_e('Could not connect to Mailjet API, please try again later!', 'mailjet-for-wordpress');
}
?>
</p>