I can not see captcha at the booking form. How to show a captcha ?
1) Go to the general booking settings page and check ON use CAPTCHA check box and save a page.
2) If you use Standard (free) version skip this step, otherwise go to the form fields customisation page add captcha shortcode to the customization form:
<p>[captcha]</p>
3) Check write permission at the folder YOUR_WORDPRES_SERVER/wp-content/plugins/booking/js/captcha/tmp/. This folder have to be writeable.
So then CPATCHA have to show up.