When I setup math captcha for Contact Form 7, the form disappears and has this error printed in its place:
Fatal error: Class ‘WPCF7_Shortcode’ not found in /home2/absbm/public_html/abmobileapps.com/wp-content/plugins/wp-math-captcha/includes/math-captcha-cf7.php on line 22
Sounds like a problem with CF7 (missing file maybe?). The error message says that one of the classes the CF7 consists of, is not available.
Math Captcha only calls this class – WPCF7_Shortcode – to extend form fields avaiable in Contact Form 7.
Does CF7 work fine on your site? Don’t you get any other error messages?