Form Submit even after the invalid value entered

Hi

I have used the Math captcha plugin with Contact form 7 but it does not show any validation error and even if I put any value not correct answer the form get submitted

See the below url:
http://zeroguess.net/011/sophiamodels/contact/

Please help and let me know what I am doing wrong.

Thanks

https://wordpress.org/plugins/wp-math-captcha/