error message: recaptcha could'nt verify private key

hello,the recaptcha on my site is not working and it is bringing up the above error message after inputting the public and private keys respective. please has any one come across this or know how to resolve this issue? -- You received this message because you are subscribed to the Google Groups "reCAPTCHA" group. To unsubscribe from this group and stop receiving emails from it, send an email to recaptcha+unsubscribe@googlegroups.com. To post to this group, send email to recaptcha@googlegroups.com. Visit this group at http://groups.google.com/group/recaptcha. For more options, visit https://groups.google.com/groups/opt_out.