The response parameter is missing.

Check your form markup to see if you have an element like on the screenshot.

#2
Unfortunately, this part is totally missing :-(
You can see here: https://comega7.hu/hu/kapcsolat

as I see it's a webform.
Did you add captcha element to the webform and choose the configured reCAPTCHA v3 action?

Okay, the Captcha element was missing, I added it, but as I see, there is no changes :-(

1. did you try to clear the cache?
2. Please show your captcha webform element configuration.
3. Are you using the custom template for this form?

1. Yes, I did.
2. Attached
3. As I see, the theme use custom twig template. Should I add captcha element there?

I think this is the custom twig file's (webform--contact_style_2.html.twig) content:

Now the code is:

<form {{ attributes }}>
        {{ element.elements.name }}
    {{ element.elements.email }}
    {{ element.elements.message }}
        {{ element.elements.actions }}
        {{ element.elements.captcha }}
        <div>
        {{ element.form_token }}
        {{ element.form_build_id }}
        {{ element.form_id }}
    </div>
</form>

It seems that is is working now. Thank you very much!!!