CF7 “Error trying to send your message”

I am using successfully Contact 7 “Contact Us” form at: https://ffscompany.com/contact-us/ and filling the form and submitting it work correctly.

I duplicated it for use as “Request A Demo” form: https://ffscompany.com/request-a-demo/

However, when “Request A Demo” is filled, I got:
“There was an error trying to send your message. Please try again later.”

What is the solution? Please advise.

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