AJAX validation is a common feature used in contact forms to validate user input without the need to refresh the entire page. This can greatly improve the user experience and make the form submission process smoother. However, sometimes, AJAX validation may not work as expected in certain WordPress themes.

One possible reason for this issue is that the necessary scripts are not properly loaded in the theme’s header. Specifically, the jQuery form library and the Contact Form 7 plugin’s JavaScript file are required for AJAX validation to work correctly.

To fix this issue, you can add the following code to the header.php file of your theme, above the closing head tag (</head>):

<script type='text/javascript' src='/wp-content/plugins/contact-form-7/includes/js/jquery.form.min.js?ver=3.40.0-2013.08.13'></script>
<script type='text/javascript'>
/* <![CDATA[ */
var _wpcf7 = {"loaderUrl":"\/wp-content\/plugins\/contact-form-7\/images\/ajax-loader.gif","sending":"Sending ..."};
/* ]]> */
<script type='text/javascript' src='/wp-content/plugins/contact-form-7/includes/js/scripts.js?ver=3.5.2'></script>

The first script tag loads the jQuery form library that is necessary for the form to be submitted correctly. The second script tag is for the Contact Form 7 plugin’s JavaScript file, which contains the AJAX validation logic.

By adding this code to your theme’s header.php file, you should properly load the necessary scripts and fix the AJAX validation issue. Keep in mind that this solution is specific to the Contact Form 7 plugin, if you are using different plugin you may need different solution.

It’s always a good idea to make a backup of your files before making any changes and test the changes on a development or staging environment before applying them to a live site. If you encounter any issues, consult the plugin’s documentation or seek help from the plugin’s support forum.