good luck on that ride, Everything has to be sent to ghl perfectly. A place to start is verifying all timezone information being passed is correct. This is where most errors happen. Another thing to check is your GHL calendar. They introduced a tool not long ago (calendar troubleshooter). The times that you think are available, may not really be available. Another item that increased my reliability is to not set and end time when booking. Set this up in your calendar and let GHL handle that.