captcha doesn't work

Hello
and first thank you for your great joola extensions!

I'm triyng to get Komento to work with captcha in the form. But the captcha is not shown with the inserted captcha. So I tried recaptcha and used it with public and private key. But also the same issue, captcha is not shown and the form is submitted without error.

In backend I enabled captcha at antispam.

Please can someone help me?

Thanks for taking time and kind regards
Beate