What does "error for site owner invalid key type recaptcha google" specifically mean?

This error message indicates that your website's Google reCAPTCHA implementation is attempting to use a key that is incompatible with the reCAPTCHA version or configuration it's trying to validate. For instance, you might be using a reCAPTCHA v3 site key for a v2 implementation (e.g., the 'I'm not a robot' checkbox), or vice-versa. It can also mean you've accidentally used a secret key where a site key is expected, or the key was generated for a different domain than the one it's being used on.