Form not submitting when recaptcha is enabled

Good day,

We have a form embedded to a landing page. We tried enabling recaptcha v3 by following these two documentations

https://experienceleague.adobe.com/en/docs/marketo/using/product-docs/demand-generation/forms/using-captcha/setting-up-recaptcha-v3

https://experienceleague.adobe.com/en/docs/marketo/using/product-docs/demand-generation/forms/using-captcha/enable-captcha-in-marketo-forms#:~:text=Click%20Edit%20Draft%20(if%20the,Click%20Finish.

But we're always getting an error "{"message":"Captcha field missing in form","error":true,"errorCode":"400"}" on the console and the form is not submitting. On the front end, it only shows "Submission failed, please try again later."