Missing Captcha image

Hi, I’m using ZenCache with Contact Form 7 and Really Simple Captcha plugins. When I use a Captcha on a form, on the mobile view no Captcha image is served up initially. Then if I enter click submit, the page reloads with a Captcha image. The Really Simple Captcha author believes this may be caused by the caching program. Is there a way to ensure that the Captchas get served when the page is loaded on mobile phones?

https://wordpress.org/plugins/zencache/