BF doesn′t register submissions and does not send out notifications

Hi! I have setup my rather simple contact form using the wizard, all settings were good to go. So far so good. Thr form itself works fine and as intended…

BUT! if anyone else but me in my local network submits the form from

https://derbandcoach.com/jetzt-buchen/

The following issues arise:

a) No submission is registered
b) No notification is sent to the WP admin (i.e. me)

Here are the settings that I have for the notification:

From Name = First and Last Name
From email = Submitter – User Email Field
To Emails = Checked WP admin box
Public submittable = Access for unregistered users checked
Enable Login on the form = None
Create an account? = Unchecked

I chose BF because it is so easy to use for such non-complex purposes that I have, and I really would like to stick to it. So, any help you could provide would be appreciated.

Thanks and regards
Sven

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