I checked it is not plugin conflict by disabling all other plugins. It was working fine before my site goes live. Now that the website is live and people try to register, they cant see the captcha block and get error on form submit "ERROR: Invalid reCAPTCHA challenge parameter.".
My keys are correct. This is very frustrating as I cant find where is the root of the problem. I check firebug DOM panel and can see the public key.
Please any help appreciated.