Google ReCaptcha

Goto click here to Google Recaptcha site and select v2 (version2)

after configuring add your site_key and secret_key admin > settings > recaptcha settings

After enabling Google ReCaptcha make sure, your credentials are correct. You will get recaptcha with the checkbox if all are correct.

For keys, click on the gear Icon (settings) > reCAPTCHA keys from google dashboard.