Failed payments for appointments shows as pending in my admin

I am configuring Appointments+ plugin. In my case payments will be required to confirm an appointment.

I have noticed that if a user fills all fields of an appointment, clicks the button to pay the appointment, but if for any reason payment fails (eg. the user closes browser tab, decides not to pay at that moment etc), I can see the appointment as pending in my admin dashboard, but the user cannot make another attempt to pay the appointment. The appointment does not show up in the user dashboard, there is no email to the user saying the appointment is pending, and I cannot re-send an email to request payment. What do I need to do?