Hello, I am using hCaptcha with UNA 13.1.0 without any issue at all. It works perfectly.

Please make sure you have entered the hCaptcha 'Site Key' and 'Secret key' correctly in UNA > Studio > Settings > Security.

The 'Site Key' (Public Key) can be found in your hCaptcha account > Sites > Settings

https://dashboard.hcaptcha.com/sites/

and

The 'Secret Key' (Private Key) can be found in your hCaptcha account > account (Top right icon) > Settings

https://dashboard.hcaptcha.com/settings

Please note that your 'Sitekey' in your hCaptcha account is your 'Public Key' in UNA and your 'Secret Key' in your hCaptcha account is the 'Private Key' in UNA.

Then save and clear your UNA cache.