Why am I getting “Input Error: K: Format Of Site Key Was Invalid”?
Why am I getting an error: "Input Error: K: Format Of Site Key Was Invalid" underneath the Security Code section of my Pro-Forms?
If you you're getting an error that says Input Error: K: Format Of Site Key Was Invalid on your s2Member Pro-Forms in the Security Code section, this indicates a problem with your CAPTCHA Anti-Spam Security configuration.
To fix this issue, visit WordPress Dashboard → s2Member (Pro) → General Options → CAPTCHA Anti-Spam Security and make sure the reCAPTCHA™ Public Key and reCAPTCHA™ Private Key fields are empty (clear them both); then click the Save All Changes button at the bottom.
Now you will need to Configure CAPTCHA Anti-Spam Security with Your Own reCAPTCHA Keys. Please follow the steps outlined in that KB article.
After following all of these steps, you should no longer be getting the Input Error: K: Format Of Site Key Was Invalid error message.