WordPress contact 7 with negative response

I have created a website using WordPress. I use a GoDaddy hosting and a plugin WP-Mail-SMTP, which helps me to configure SMTP. I have disable all cache plugins.

Right now I have a problem with my contact form (plugin Contact form 7). When I fill all fields and click a submit button, I get messages: "There was an error trying to send your message. Please try again later."

I get next JSON answer from my server:

captcha:null
into:"#wpcf7-f31-p1401-o1"
mailSent: false
message: "There was an error trying to send your message. Please try again later."

I receive emails from this forms, but I can not fix issues with server response and negative answers under my form: https://www.screencast.com/t/ReyXMwJLRS. I try to disable/enable captcha, but it does not help.

Can somebody advice with this. I have checked all recommendation from https://contactform7.com/, but can not find a solution.

Best regards.