On picking up car and proceeding to exit barrier the car in front could not get through as his ticket was returned and exit denied. He then exited his car to troubleshoot with the office thus blocking me. Eventually he returned and on presenting his ticket the barrier was raised and on he went. I next in line issued my ticket and exit was denied, with no one behind me i was able to reverse back alongside the office to find out why. Apparently we were told the other guys registration was entered wrong but then why was I denied when the registration was entered on the documentation correctly. Not what you want after a plane journey and all you want to do is get home