Not working for for the users

Hi there,
On the page is this not working i used Chrome, Safari browser:
Make Bookings on Client side:

Client can add new appoinments.
Show booked appointments on Calender. So client can change appoinment.
client can manage appointments.
Email send automatically when client add appoinment.

In Admin:
Appointments Book: settings are not working

https://wordpress.org/plugins/appointment-book/