Webform issue with captcha
I don't think reCAPTCHA module provides front-end validation. Have you tried performing front-end validation using reCAPTCHA API? You could try something like this:

 $('form').submit(function () {
   if (!grecaptcha.getResponse()) {
     event.preventDefault();
     $('&lt;span class="red recaptcha"&gt;reCAPTCHA is invalid&lt;/span&gt;').insertAfter('.g-recaptcha');}
  });