wp-json/contact-form-7/v1/contact-forms/39043/feedback Return 409

I’m cannot send any comment if I am not logged in. Using both an admin and a normal user account, the test comment is sending.

I’m using CF7 v5.14 and WordPress v5.2.2

When I try to send a comment and I’m logged in the following message appears: “Failed to load resource: the server responded with a status of 409” and this link: https://cmplastico.com.br/wp-json/contact-form-7/v1/contact-forms/6/feedback

Please let me know how can we solve this error.

The page I need help with: [log in to see the link]