Appointments+ "Please click here to confirm" button doesn't do anything (although the

When I click on the "Please click here to confirm this appointment" the appointment is recorded in the back end and the emails are sent out but the page doesn't respond (the little "spinner" spins beside the cancel button but the page doesn't advance or go anywhere). I can't figure out what setting I've messed up or if this is something else. Any advice would be appreciated. Thanks.