Sent to a 404 page when cancelling appointment booking form

I just updated to the newest version of Appointments+ and then went to test the bookings form at my site: http://www.kogawahouse.com/wp/tours/book-a-tour/

I clicked on an appointment date and time and the booking form appeared, so that all seemed fine. I then clicked "Cancel" on the form and was sent to a 404 page with the URL http://www.kogawahouse.com/wp/tours/book-a-tour/undefined

Can you please help? I have enabled support access just in case.