CS Forms - nothing happens at form submission

Hi there,
what I’m doing wrong?

I’ve set-tup a Email action, but after submitting the form, nothing happens. I do not get any email, and also no submission is stored in Cornerstone->Form Submissions.
I have activate Form Submissions and set-up the Email Action, I’m also using Fluent SMTP and usually have no problems.

I followed the this Video-Tutorial.

If you need access to my WP, take I provided my data here.

Thanks!