Error 403

Good day,

We use their plugin Frontend Admin for our internal team system.

When creating a form with “New User Form” an error occurs.
After trying to create a new user in the frontend, Server Error 403 comes up.
See screenshot.

We don’t know what’s ahead, do you have a solution?

Have a nice day.

greeting
TiM2760

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