Spam error after including reCAPTCHA

Hello,
I have problem with newest plugin version. Akismet plugin is disabled and Comment Blacklist is empty.
After adding recaptcha to my form i receive error message: Failed to send your message. Please try later or contact the administrator by another method.
There is a content of response: {“mailSent”:false,”into”:”#wpcf7-f19-p13-o1″,”captcha”:null,”message”:”Failed to send your message. Please try later or contact the administrator by another method.”,”spam”:true}.
Why key spam is set to true? How to solve my problem?

Thanks.

https://wordpress.org/plugins/contact-form-7/