notification an form sent does not work

Hello together,
I do not receive e-mail notifications when the form has been filled out and sent by a user. I only can find it in the formcraft basic dashboard under submissions.

The text I have created under custom messages in the form sent field is not shown at the page when the form has successfully been transmitted by a client (that means I can see it under submissions in the plugins dashboad). That is very unlucky, if the form user does no receive a notice from me.

By the way, with the validation errors text everthing is ok.

Would be very thankful for any help.

Claudia