a problem in appointments plugin

Hi
I have discovered a problem in appointment +.
I have created an user and i enter in another browser this user in order to get an appointment. I followed all the steps and when i've tried to pay the appointment through "paypal sandbox" i couldnt do it because my settings were wrong set in the admin page, but this wasnt the problem.

The problem comes when (after solving the problem in my paypal sandbox settings) i ( as a ficticious user) try to get another appointment, and the system tells me that i have a pending appointment. And thats not true because if i go to the admin page to look for this appointment ( in appointments tab) there is nothing.

So this is the problem, the user cant get another appointment and i ( as a admin) cant see if somebody has a pending appointment to cancel it in order to let the user get another appointment.

I dont know if i do you understand me? is a little complex.