i am using chronform5 on joomla 3.6.5 and create new form with captcha. but the captcha image doesn't show the front end.
This FAQ has some suggestions to try if you have added a Captcha element to your form with the Load Captcha and Check Captcha actions but the image is not displaying.
{captcha_img}

It looks as though you have added both Captcha and ReCaptcha elements in your form - you only need one of them; and the corresponding Load action needs to be in the form On Load event before the HTML (render form) action.