After 2.3.3 version updated Recaptcha not working in localhost but working fine in live server. now we using silverstripe 2.4.0(latest version) still same issue came. Please find the screenshot for your reference. Let me know if you find any solutions.
[User Error] RecatpchaField::validate(): Recaptcha-service error: ''Input error: response: Required field must not be blank\nchallenge: Required field must not be blank\n''