Why does my Cloud reCAPTCHA checkbox say the site key is missing?

First, check that the key in the Cloud console is actually a challenge checkbox key, not a score-based key. Then check that the page passes that site key to the widget and loads the script intended for the integration you're using.

If you're using the Enterprise integration, that means checking enterprise.js rather than assuming the classic api.js setup applies. A data-action value such as LOGIN belongs to score-based integrations, so remove it from a checkbox widget and make sure the key type and rendering code match. The error alone doesn't prove which part is wrong, but those are useful places to start.

Cloudflare Turnstile is worth a look if you're ready to replace reCAPTCHA rather than spend more time on this migration. You'll still need to integrate and verify its responses, so it isn't necessarily a drop-in fix.

Private Captcha has a reCAPTCHA compatibility mode, which may make migration easier. Check its migration documentation against your current client and server integration before assuming a script swap is all you'll need.

A score-based key is another option if you don't specifically need a checkbox challenge. It uses a different integration, though, so switching key types without changing the corresponding code won't necessarily resolve the site key error.