You got an error message:
"Invalid site key. Please see the FAQ."

It is probably about recaptcha wrong key. Possible solution can be to go to

and add your site. You will get:
- Site key
- Secret key

use these in your content management system

I have Joomla and i had to login Joomla admin control panel and then click: Community builder, Plugin management, CBreCaptcha and update the keys here.